Skip to main content
Chemistry LibreTexts


  • Page ID
  • \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

    \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)

    \( \newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\)

    ( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\)

    \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

    \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\)

    \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)

    \( \newcommand{\Span}{\mathrm{span}}\)

    \( \newcommand{\id}{\mathrm{id}}\)

    \( \newcommand{\Span}{\mathrm{span}}\)

    \( \newcommand{\kernel}{\mathrm{null}\,}\)

    \( \newcommand{\range}{\mathrm{range}\,}\)

    \( \newcommand{\RealPart}{\mathrm{Re}}\)

    \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

    \( \newcommand{\Argument}{\mathrm{Arg}}\)

    \( \newcommand{\norm}[1]{\| #1 \|}\)

    \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)

    \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)

    \( \newcommand{\vectorA}[1]{\vec{#1}}      % arrow\)

    \( \newcommand{\vectorAt}[1]{\vec{\text{#1}}}      % arrow\)

    \( \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

    \( \newcommand{\vectorC}[1]{\textbf{#1}} \)

    \( \newcommand{\vectorD}[1]{\overrightarrow{#1}} \)

    \( \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} \)

    \( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)

    \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

    \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)


     Example and Directions
    Words (or words that have the same definition) The definition is case sensitive (Optional) Image to display with the definition [Not displayed in Glossary, only in pop-up on pages] (Optional) Caption for Image (Optional) External or Internal Link (Optional) Source for Definition
    (Eg. "Genetic, Hereditary, DNA ...") (Eg. "Relating to genes or heredity") Green DNA Strand The infamous double helix Biology CC-BY-SA; Delmar Larsen
    Glossary Entries



    Image Caption Link Source
    chemistry study of the composition, properties, and interactions of matter        
    hypothesis tentative explanation of observations that acts as a guide for gathering and checking information        
    law statement that summarizes a vast number of experimental observations, and describes or predicts some aspect of the natural world        
    macroscopic domain realm of everyday things that are large enough to sense directly by human sight and touch        
    microscopic domain realm of things that are much too small to be sensed directly        
    scientific method path of discovery that leads from question and observation to law or hypothesis to theory, combined with experimental verification of the hypothesis and any necessary modification of the theory        
    symbolic domain specialized language used to represent components of the macroscopic and microscopic domains, such as chemical symbols, chemical formulas, chemical equations, graphs, drawings, and calculations        
    theory well-substantiated, comprehensive, testable explanation of a particular aspect of nature        
    atom smallest particle of an element that can enter into a chemical combination        
    compound pure substance that can be decomposed into two or more elements        
    element substance that is composed of a single type of atom; a substance that cannot be decomposed by a chemical change        
    gas state in which matter has neither definite volume nor shape        
    heterogeneous mixture combination of substances with a composition that varies from point to point        
    homogeneous mixture (also, solution) combination of substances with a composition that is uniform throughout        
    liquid state of matter that has a definite volume but indefinite shape        
    law of conservation of matter when matter converts from one type to another or changes form, there is no detectable change in the total amount of matter present        
    mass fundamental property indicating amount of matter        
    matter anything that occupies space and has mass        
    mixture matter that can be separated into its components by physical means        
    molecule bonded collection of two or more atoms of the same or different elements        
    plasma gaseous state of matter containing a large number of electrically charged atoms and/or molecules        
    pure substance homogeneous substance that has a constant composition        
    solid state of matter that is rigid, has a definite shape, and has a fairly constant volume        
    weight force that gravity exerts on an object        
    chemical change change producing a different kind of matter from the original kind of matter        
    chemical property behavior that is related to the change of one kind of matter into another kind of matter        
    extensive property property of a substance that depends on the amount of the substance        
    intensive property property of a substance that is independent of the amount of the substance        
    physical change change in the state or properties of matter that does not involve a change in its chemical composition        
    physical property characteristic of matter that is not associated with any change in its chemical composition        
    Celsius (°C) unit of temperature; water freezes at 0 °C and boils at 100 °C on this scale        
    cubic centimeter (cm3 or cc) volume of a cube with an edge length of exactly 1 cm        
    cubic meter (m3) SI unit of volume        
    density ratio of mass to volume for a substance or object        
    kelvin (K) SI unit of temperature; 273.15 K = 0 ºC        
    kilogram (kg) standard SI unit of mass; 1 kg = approximately 2.2 pounds        
    length measure of one dimension of an object        
    liter (L) (also, cubic decimeter) unit of volume; 1 L = 1,000 cm3        
    meter (m) standard metric and SI unit of length; 1 m = approximately 1.094 yards        
    milliliter (mL) 1/1,000 of a liter; equal to 1 cm3        
    second (s) SI unit of time        
    SI units (International System of Units) standards fixed by international agreement in the International System of Units (Le Système International d’Unités)        
    unit standard of comparison for measurements        
    volume amount of space occupied by an object        
    uncertainty estimate of amount by which measurement differs from true value        
    significant figures (also, significant digits) all of the measured digits in a determination, including the uncertain last digit        
    rounding procedure used to ensure that calculated results properly reflect the uncertainty in the measurements used in the calculation        
    precision how closely a measurement matches the same measurement when repeated        
    exact number number derived by counting or by definition        
    accuracy how closely a measurement aligns with a correct value        
    dimensional analysis (also, factor-label method) versatile mathematical approach that can be applied to computations ranging from simple unit conversions to more complex, multi-step calculations involving several different quantities        
    Fahrenheit unit of temperature; water freezes at 32 °F and boils at 212 °F on this scale        
    unit conversion factor ratio of equivalent quantities expressed with different units; used to convert from one unit to a different unit        
    Dalton’s atomic theory set of postulates that established the fundamental properties of atoms        
    law of constant composition (also, law of definite proportions) all samples of a pure compound contain the same elements in the same proportions by mass        
    law of multiple proportions when two elements react to form more than one compound, a fixed mass of one element will react with masses of the other element in a ratio of small whole numbers        
    law of definite proportions (also, law of constant composition) all samples of a pure compound contain the same elements in the same proportions by mass        
    alpha particle (α particle) positively charged particle consisting of two protons and two neutrons        
    electron negatively charged, subatomic particle of relatively low mass located outside the nucleus        
    isotopes atoms that contain the same number of protons but different numbers of neutrons        
    neutron uncharged, subatomic particle located in the nucleus        
    proton positively charged, subatomic particle located in the nucleus        
    nucleus massive, positively charged center of an atom made up of protons and neutrons        
    anion negatively charged atom or molecule (contains more electrons than protons)        
    atomic mass average mass of atoms of an element, expressed in amu        
    atomic mass unit (amu) (also, unified atomic mass unit, u, or Dalton, Da) unit of mass equal to \(\dfrac{1}{12}\) of the mass of a 12C atom        
    atomic number (Z) number of protons in the nucleus of an atom        
    cation positively charged atom or molecule (contains fewer electrons than protons)        
    chemical symbol one-, two-, or three-letter abbreviation used to represent an element or its atoms        
    Dalton (Da) alternative unit equivalent to the atomic mass unit        
    fundamental unit of charge (also called the elementary charge) equals the magnitude of the charge of an electron (e) with e = 1.602 \(\times\) 10−19 C        
    ion electrically charged atom or molecule (contains unequal numbers of protons and electrons)        
    mass number (A) sum of the numbers of neutrons and protons in the nucleus of an atom        
    unified atomic mass unit (u) alternative unit equivalent to the atomic mass unit        
    empirical formula formula showing the composition of a compound given as the simplest whole-number ratio of atoms        
    isomers compounds with the same chemical formula but different structures        
    molecular formula formula indicating the composition of a molecule of a compound and giving the actual number of atoms of each element in a molecule of the compound.        
    spatial isomers compounds in which the relative orientations of the atoms in space differ        
    structural isomer one of two substances that have the same molecular formula but different physical and chemical properties because their atoms are bonded differently        
    structural formula shows the atoms in a molecule and how they are connected        
    actinide inner transition metal in the bottom of the bottom two rows of the periodic table        
    alkali metal element in group 1        
    alkaline earth metal element in group 2        
    chalcogen element in group 16        
    group vertical column of the periodic table        
    halogen element in group 17        
    inert gas (also, noble gas) element in group 18        
    inner transition metal (also, lanthanide or actinide) element in the bottom two rows; if in the first row, also called lanthanide, or if in the second row, also called actinide        
    lanthanide inner transition metal in the top of the bottom two rows of the periodic table        
    main-group element (also, representative element) element in columns 1, 2, and 12–18        
    metal element that is shiny, malleable, good conductor of heat and electricity        
    metalloid element that conducts heat and electricity moderately well, and possesses some properties of metals and some properties of nonmetals        
    noble gas (also, inert gas) element in group 18        
    nonmetal element that appears dull, poor conductor of heat and electricity        
    period (also, series) horizontal row of the periodic table        
    periodic law properties of the elements are periodic function of their atomic numbers.        
    periodic table table of the elements that places elements with similar chemical properties close together        
    pnictogen element in group 15        
    representative element (also, main-group element) element in columns 1, 2, and 12–18        
    transition metal element in columns 3–11        
    series (also, period) horizontal row of the period table        
    covalent bond attractive force between the nuclei of a molecule’s atoms and pairs of electrons between the atoms        
    covalent compound (also, molecular compound) composed of molecules formed by atoms of two or more different elements        
    ionic bond electrostatic forces of attraction between the oppositely charged ions of an ionic compound        
    ionic compound compound composed of cations and anions combined in ratios, yielding an electrically neutral substance        
    molecular compound (also, covalent compound) composed of molecules formed by atoms of two or more different elements        
    monatomic ion ion composed of a single atom        
    polyatomic ion ion composed of more than one atom        
    oxyanion polyatomic anion composed of a central atom bonded to oxygen atoms        
    binary acid compound that contains hydrogen and one other element, bonded in a way that imparts acidic properties to the compound (ability to release H+ ions when dissolved in water)        
    binary compound compound containing two different elements.        
    oxyacid compound that contains hydrogen, oxygen, and one other element, bonded in a way that imparts acidic properties to the compound (ability to release H+ ions when dissolved in water)        
    nomenclature system of rules for naming objects of interest        
    Avogadro’s number (NA) experimentally determined value of the number of entities comprising 1 mole of substance, equal to 6.022 × 1023 mol−1        
    formula mass sum of the average masses for all atoms represented in a chemical formula; for covalent compounds, this is also the molecular mass        
    mole amount of substance containing the same number of atoms, molecules, ions, or other entities as the number of atoms in exactly 12 grams of 12C        
    molar mass mass in grams of 1 mole of a substance        
    percent composition percentage by mass of the various elements in a compound        
    empirical formula mass sum of average atomic masses for all atoms represented in an empirical formula        
    aqueous solution solution for which water is the solvent        
    concentrated qualitative term for a solution containing solute at a relatively high concentration        
    concentration quantitative measure of the relative amounts of solute and solvent present in a solution        
    dilute qualitative term for a solution containing solute at a relatively low concentration        
    dilution process of adding solvent to a solution in order to lower the concentration of solutes        
    dissolved describes the process by which solute components are dispersed in a solvent        
    molarity (M) unit of concentration, defined as the number of moles of solute dissolved in 1 liter of solution        
    solute solution component present in a concentration less than that of the solvent        
    solvent solution component present in a concentration that is higher relative to other components        
    mass percentage ratio of solute-to-solution mass expressed as a percentage        
    mass-volume percent ratio of solute mass to solution volume, expressed as a percentage        
    parts per billion (ppb) ratio of solute-to-solution mass multiplied by 109        
    parts per million (ppm) ratio of solute-to-solution mass multiplied by 106        
    volume percentage ratio of solute-to-solution volume expressed as a percentage        
    balanced equation chemical equation with equal numbers of atoms for each element in the reactant and product        
    chemical equation symbolic representation of a chemical reaction        
    coefficient number placed in front of symbols or formulas in a chemical equation to indicate their relative amount        
    complete ionic equation chemical equation in which all dissolved ionic reactants and products, including spectator ions, are explicitly represented by formulas for their dissociated ions        
    molecular equation chemical equation in which all reactants and products are represented as neutral substances        
    net ionic equation chemical equation in which only those dissolved ionic reactants and products that undergo a chemical or physical change are represented (excludes spectator ions)        
    product substance formed by a chemical or physical change; shown on the right side of the arrow in a chemical equation        
    reactant substance undergoing a chemical or physical change; shown on the left side of the arrow in a chemical equation        
    spectator ion ion that does not undergo a chemical or physical change during a reaction, but its presence is required to maintain charge neutrality        
    actual yield amount of product formed in a reaction        
    excess reactant reactant present in an amount greater than required by the reaction stoichiometry        
    limiting reactant reactant present in an amount lower than required by the reaction stoichiometry, thus limiting the amount of product generated        
    percent yield measure of the efficiency of a reaction, expressed as a percentage of the theoretical yield        
    theoretical yield amount of product that may be produced from a given amount of reactant(s) according to the reaction stoichiometry        
    analyte chemical species of interest        
    buret device used for the precise delivery of variable liquid volumes, such as in a titration analysis        
    combustion analysis gravimetric technique used to determine the elemental composition of a compound via the collection and weighing of its gaseous combustion products        
    end point measured volume of titrant solution that yields the change in sample solution appearance or other property expected for stoichiometric equivalence (see equivalence point)        
    equivalence point volume of titrant solution required to react completely with the analyte in a titration analysis; provides a stoichiometric amount of titrant for the sample’s analyte according to the titration reaction        
    gravimetric analysis quantitative chemical analysis method involving the separation of an analyte from a sample by a physical or chemical process and subsequent mass measurements of the analyte, reaction product, and/or sample        
    indicator substance added to the sample in a titration analysis to permit visual detection of the end point        
    quantitative analysis the determination of the amount or concentration of a substance in a sample        
    titrant solution containing a known concentration of substance that will react with the analyte in a titration analysis        
    titration analysis quantitative chemical analysis method that involves measuring the volume of a reactant solution required to completely react with the analyte in a sample        
    calorie (cal) unit of heat or other energy; the amount of energy required to raise 1 gram of water by 1 degree Celsius; 1 cal is defined as 4.184 J        
    endothermic process chemical reaction or physical change that absorbs heat        
    energy capacity to supply heat or do work        
    exothermic process chemical reaction or physical change that releases heat        
    heat (q) transfer of thermal energy between two bodies        
    heat capacity (C) extensive property of a body of matter that represents the quantity of heat required to increase its temperature by 1 degree Celsius (or 1 kelvin)        
    joule (J) SI unit of energy; 1 joule is the kinetic energy of an object with a mass of 2 kilograms moving with a velocity of 1 meter per second, 1 J = 1 kg m2/s and 4.184 J = 1 cal        
    kinetic energy energy of a moving body, in joules, equal to \(\dfrac{1}{2}mv^2\) (where m = mass and v = velocity)        
    potential energy energy of a particle or system of particles derived from relative position, composition, or condition        
    specific heat capacity (c) intensive property of a substance that represents the quantity of heat required to raise the temperature of 1 gram of the substance by 1 degree Celsius (or 1 kelvin)        
    temperature intensive property of matter that is a quantitative measure of “hotness” and “coldness”        
    thermal energy kinetic energy associated with the random motion of atoms and molecules        
    thermochemistry study of measuring the amount of heat absorbed or released during a chemical reaction or a physical change        
    work (w) energy transfer due to changes in external, macroscopic variables such as pressure and volume; or causing matter to move against an opposing force        
    bomb calorimeter device designed to measure the energy change for processes occurring under conditions of constant volume; commonly used for reactions involving solid and gaseous reactants or products        
    calorimeter device used to measure the amount of heat absorbed or released in a chemical or physical process        
    calorimetry process of measuring the amount of heat involved in a chemical or physical process        
    nutritional calorie (Calorie) unit used for quantifying energy provided by digestion of foods, defined as 1000 cal or 1 kcal        
    surroundings all matter other than the system being studied        
    system portion of matter undergoing a chemical or physical change being studied        
    chemical thermodynamics area of science that deals with the relationships between heat, work, and all forms of energy associated with chemical and physical processes        
    enthalpy (H) sum of a system’s internal energy and the mathematical product of its pressure and volume        
    enthalpy change (ΔH) heat released or absorbed by a system under constant pressure during a chemical or physical process        
    expansion work (pressure-volume work) work done as a system expands or contracts against external pressure        
    first law of thermodynamics internal energy of a system changes due to heat flow in or out of the system or work done on or by the system        
    Hess’s law if a process can be represented as the sum of several steps, the enthalpy change of the process equals the sum of the enthalpy changes of the steps        
    hydrocarbon compound composed only of hydrogen and carbon; the major component of fossil fuels        
    internal energy (U) total of all possible kinds of energy present in a substance or substances        
    standard enthalpy of combustion (\(ΔH^\circ_\ce{c}\)) heat released when one mole of a compound undergoes complete combustion under standard conditions        
    standard enthalpy of formation (\(ΔH^\circ_\ce{f}\)) enthalpy change of a chemical reaction in which 1 mole of a pure substance is formed from its elements in their most stable states under standard state conditions        
    standard state set of physical conditions as accepted as common reference conditions for reporting thermodynamic properties; 1 bar of pressure, and solutions at 1 molar concentrations, usually at a temperature of 298.15 K        
    state function property depending only on the state of a system, and not the path taken to reach that state        
    amplitude extent of the displacement caused by a wave (for sinusoidal waves, it is one-half the difference from the peak height to the trough depth, and the intensity is proportional to the square of the amplitude)        
    blackbody idealized perfect absorber of all incident electromagnetic radiation; such bodies emit electromagnetic radiation in characteristic continuous spectra called blackbody radiation        
    continuous spectrum electromagnetic radiation given off in an unbroken series of wavelengths (e.g., white light from the sun)        
    electromagnetic radiation energy transmitted by waves that have an electric-field component and a magnetic-field component        
    electromagnetic spectrum range of energies that electromagnetic radiation can comprise, including radio, microwaves, infrared, visible, ultraviolet, X-rays, and gamma rays; since electromagnetic radiation energy is proportional to the frequency and inversely proportional to the wavelength, the spectrum can also be specified by ranges of frequencies or wavelengths        
    frequency (\(\nu\)) number of wave cycles (peaks or troughs) that pass a specified point in space per unit time        
    hertz (Hz) the unit of frequency, which is the number of cycles per second, s−1        
    intensity property of wave-propagated energy related to the amplitude of the wave, such as brightness of light or loudness of sound        
    interference pattern pattern typically consisting of alternating bright and dark fringes; it results from constructive and destructive interference of waves        
    line spectrum electromagnetic radiation emitted at discrete wavelengths by a specific atom (or atoms) in an excited state        
    node any point of a standing wave with zero amplitude        
    photon smallest possible packet of electromagnetic radiation, a particle of light        
    quantization occurring only in specific discrete values, not continuous        
    standing wave (also, stationary wave) localized wave phenomenon characterized by discrete wavelengths determined by the boundary conditions used to generate the waves; standing waves are inherently quantized        
    wave oscillation that can transport energy from one point to another in space        
    wavelength (λ) distance between two consecutive peaks or troughs in a wave        
    wave-particle duality term used to describe the fact that elementary particles including matter exhibit properties of both particles (including localized position, momentum) and waves (including nonlocalization, wavelength, frequency)        
    Bohr’s model of the hydrogen atom structural model in which an electron moves around the nucleus only in circular orbits, each with a specific allowed radius; the orbiting electron does not normally emit electromagnetic radiation, but does so when changing from one orbit to another.        
    excited state state having an energy greater than the ground-state energy        
    ground state state in which the electrons in an atom, ion, or molecule have the lowest energy possible        
    quantum number integer number having only specific allowed values and used to characterize the arrangement of electrons in an atom        
    angular momentum quantum number (l) quantum number distinguishing the different shapes of orbitals; it is also a measure of the orbital angular momentum        
    atomic orbital mathematical function that describes the behavior of an electron in an atom (also called the wavefunction), it can be used to find the probability of locating an electron in a specific region around the nucleus, as well as other dynamical variables        
    d orbital region of space with high electron density that is either four lobed or contains a dumbbell and torus shape; describes orbitals with l = 2. An electron in this orbital is called a d electron        
    electron density a measure of the probability of locating an electron in a particular region of space, it is equal to the squared absolute value of the wave function ψ        
    f orbital multilobed region of space with high electron density, describes orbitals with l = 3. An electron in this orbital is called an f electron        
    Heisenberg uncertainty principle rule stating that it is impossible to exactly determine both certain conjugate dynamical properties such as the momentum and the position of a particle at the same time. The uncertainty principle is a consequence of quantum particles exhibiting wave–particle duality        
    magnetic quantum number (ml) quantum number signifying the orientation of an atomic orbital around the nucleus; orbitals having different values of ml but the same subshell value of l have the same energy (are degenerate), but this degeneracy can be removed by application of an external magnetic field        
    p orbital dumbbell-shaped region of space with high electron density, describes orbitals with l = 1. An electron in this orbital is called a p electron        
    Pauli exclusion principle specifies that no two electrons in an atom can have the same value for all four quantum numbers        
    principal quantum number (n) quantum number specifying the shell an electron occupies in an atom        
    quantum mechanics field of study that includes quantization of energy, wave-particle duality, and the Heisenberg uncertainty principle to describe matter        
    s orbital spherical region of space with high electron density, describes orbitals with l = 0. An electron in this orbital is called an s electron        
    shell set of orbitals with the same principal quantum number, n        
    spin quantum number (ms) number specifying the electron spin direction, either \(+\dfrac{1}{2}\) or \(−\dfrac{1}{2}\)        
    subshell set of orbitals in an atom with the same values of n and l        
    wavefunction (ψ) mathematical description of an atomic orbital that describes the shape of the orbital; it can be used to calculate the probability of finding the electron at any given location in the orbital, as well as dynamical variables such as the energy and the angular momentum        
    Aufbau principle procedure in which the electron configuration of the elements is determined by “building” them in order of atomic numbers, adding one proton to the nucleus and one electron to the proper subshell at a time        
    core electron electron in an atom that occupies the orbitals of the inner shells        
    electron configuration electronic structure of an atom in its ground state given as a listing of the orbitals occupied by the electrons        
    Hund’s rule every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied, and all electrons in singly occupied orbitals have the same spin        
    orbital diagram pictorial representation of the electron configuration showing each orbital as a box and each electron as an arrow        
    valence electrons electrons in the outermost or valence shell (highest value of n) of a ground-state atom; determine how an element reacts        
    valence shell outermost shell of electrons in a ground-state atom; for main group elements, the orbitals with the highest n level (s and p subshells) are in the valence shell, while for transition metals, the highest energy s and d subshells make up the valence shell and for inner transition elements, the highest s, d, and f subshells are included        
    covalent radius one-half the distance between the nuclei of two identical atoms when they are joined by a covalent bond        
    effective nuclear charge charge that leads to the Coulomb force exerted by the nucleus on an electron, calculated as the nuclear charge minus shielding        
    electron affinity energy required to add an electron to a gaseous atom to form an anion        
    ionization energy energy required to remove an electron from a gaseous atom or ion. The associated number (e.g., second ionization energy) corresponds to the charge of the ion produced (X2+)        
    isoelectronic group of ions or atoms that have identical electron configurations        
    inert pair effect tendency of heavy atoms to form ions in which their valence s electrons are not lost        
    ionic bond strong electrostatic force of attraction between cations and anions in an ionic compound        
    bond length distance between the nuclei of two bonded atoms at which the lowest potential energy is achieved        
    covalent bond bond formed when electrons are shared between atoms        
    electronegativity tendency of an atom to attract electrons in a bond to itself        
    polar covalent bond covalent bond between atoms of different electronegativities; a covalent bond with a positive end and a negative end        
    pure covalent bond (also, nonpolar covalent bond) covalent bond between atoms of identical electronegativities        
    double bond covalent bond in which two pairs of electrons are shared between two atoms        
    free radical molecule that contains an odd number of electrons        
    hypervalent molecule molecule containing at least one main group element that has more than eight electrons in its valence shell        
    Lewis structure diagram showing lone pairs and bonding pairs of electrons in a molecule or an ion        
    Lewis symbol symbol for an element or monatomic ion that uses a dot to represent each valence electron in the element or ion        
    lone pair two (a pair of) valence electrons that are not used to form a covalent bond        
    octet rule guideline that states main group atoms will form structures in which eight valence electrons interact with each nucleus, counting bonding electrons as interacting with both atoms connected by the bond        
    single bond bond in which a single pair of electrons is shared between two atoms        
    triple bond bond in which three pairs of electrons are shared between two atoms        
    formal charge charge that would result on an atom by taking the number of valence electrons on the neutral atom and subtracting the nonbonding electrons and the number of bonds (one-half of the bonding electrons)        
    molecular structure arrangement of atoms in a molecule or ion        
    resonance situation in which one Lewis structure is insufficient to describe the bonding in a molecule and the average of multiple structures is observed        
    resonance forms two or more Lewis structures that have the same arrangement of atoms but different arrangements of electrons        
    resonance hybrid average of the resonance forms shown by the individual Lewis structures        
    bond energy (also, bond dissociation energy) energy required to break a covalent bond in a gaseous substance        
    Born-Haber cycle thermochemical cycle relating the various energetic steps involved in the formation of an ionic solid from the relevant elements        
    lattice energy (ΔHlattice) energy required to separate one mole of an ionic solid into its component gaseous ions        
    axial position location in a trigonal bipyramidal geometry in which there is another atom at a 180° angle and the equatorial positions are at a 90° angle        
    bond angle angle between any two covalent bonds that share a common atom        
    bond distance (also, bond length) distance between the nuclei of two bonded atoms        
    bond dipole moment separation of charge in a bond that depends on the difference in electronegativity and the bond distance represented by partial charges or a vector        
    dipole moment property of a molecule that describes the separation of charge determined by the sum of the individual bond moments based on the molecular structure        
    electron-pair geometry arrangement around a central atom of all regions of electron density (bonds, lone pairs, or unpaired electrons)        
    equatorial position one of the three positions in a trigonal bipyramidal geometry with 120° angles between them; the axial positions are located at a 90° angle        
    linear shape in which two outside groups are placed on opposite sides of a central atom        
    molecular structure structure that includes only the placement of the atoms in the molecule        
    octahedral shape in which six outside groups are placed around a central atom such that a three-dimensional shape is generated with four groups forming a square and the other two forming the apex of two pyramids, one above and one below the square plane        
    polar molecule (also, dipole) molecule with an overall dipole moment        
    tetrahedral shape in which four outside groups are placed around a central atom such that a three-dimensional shape is generated with four corners and 109.5° angles between each pair and the central atom        
    trigonal bipyramidal shape in which five outside groups are placed around a central atom such that three form a flat triangle with 120° angles between each pair and the central atom, and the other two form the apex of two pyramids, one above and one below the triangular plane        
    trigonal planar shape in which three outside groups are placed in a flat triangle around a central atom with 120° angles between each pair and the central atom        
    valence shell electron-pair repulsion theory ( VSEPR) theory used to predict the bond angles in a molecule based on positioning regions of high electron density as far apart as possible to minimize electrostatic repulsion        
    vector quantity having magnitude and direction        
    overlap coexistence of orbitals from two different atoms sharing the same region of space, leading to the formation of a covalent bond        
    node plane separating different lobes of orbitals, where the probability of finding an electron is zero        
    pi bond (π bond) covalent bond formed by side-by-side overlap of atomic orbitals; the electron density is found on opposite sides of the internuclear axis        
    sigma bond (σ bond) covalent bond formed by overlap of atomic orbitals along the internuclear axis        
    valence bond theory description of bonding that involves atomic orbitals overlapping to form σ or π bonds, within which pairs of electrons are shared        
    atmosphere (atm) unit of pressure; 1 atm = 101,325 Pa        
    bar (bar or b) unit of pressure; 1 bar = 100,000 Pa        
    barometer device used to measure atmospheric pressure        
    hydrostatic pressure pressure exerted by a fluid due to gravity        
    manometer device used to measure the pressure of a gas trapped in a container        
    pascal (Pa) SI unit of pressure; 1 Pa = 1 N/m2        
    pounds per square inch (psi) unit of pressure common in the US        
    pressure force exerted per unit area        
    torr unit of pressure; \(\mathrm{1\: torr=\dfrac{1}{760}\,atm}\)        
    compressibility factor (Z) ratio of the experimentally measured molar volume for a gas to its molar volume as computed from the ideal gas equation        
    van der Waals equation modified version of the ideal gas equation containing additional terms to account for non-ideal gas behavior        
    dipole-dipole attraction intermolecular attraction between two permanent dipoles        
    dispersion force (also, London dispersion force) attraction between two rapidly fluctuating, temporary dipoles; significant only when particles are very close together        
    hydrogen bonding occurs when exceptionally strong dipoles attract; bonding that exists when hydrogen is bonded to one of the three most electronegative elements: F, O, or N        
    induced dipole temporary dipole formed when the electrons of an atom or molecule are distorted by the instantaneous dipole of a neighboring atom or molecule        
    instantaneous dipole temporary dipole that occurs for a brief moment in time when the electrons of an atom or molecule are distributed asymmetrically        
    intermolecular force noncovalent attractive force between atoms, molecules, and/or ions        
    polarizability measure of the ability of a charge to distort a molecule’s charge distribution (electron cloud)        
    van der Waals force attractive or repulsive force between molecules, including dipole-dipole, dipole-induced dipole, and London dispersion forces; does not include forces due to covalent or ionic bonding, or the attraction between ions and molecules        
    adhesive force force of attraction between molecules of different chemical identities        
    capillary action flow of liquid within a porous material due to the attraction of the liquid molecules to the surface of the material and to other liquid molecules        
    cohesive force force of attraction between identical molecules        
    surface tension energy required to increase the area, or length, of a liquid surface by a given amount        
    viscosity measure of a liquid’s resistance to flow        
    boiling point temperature at which the vapor pressure of a liquid equals the pressure of the gas above it        
    Clausius-Clapeyron equation mathematical relationship between the temperature, vapor pressure, and enthalpy of vaporization for a substance        
    condensation change from a gaseous to a liquid state        
    deposition change from a gaseous state directly to a solid state        
    dynamic equilibrium state of a system in which reciprocal processes are occurring at equal rates        
    freezing change from a liquid state to a solid state        
    freezing point temperature at which the solid and liquid phases of a substance are in equilibrium; see also melting point        
    melting change from a solid state to a liquid state        
    melting point temperature at which the solid and liquid phases of a substance are in equilibrium; see also freezing point        
    normal boiling point temperature at which a liquid’s vapor pressure equals 1 atm (760 torr)        
    sublimation change from solid state directly to gaseous state        
    vapor pressure (also, equilibrium vapor pressure) pressure exerted by a vapor in equilibrium with a solid or a liquid at a given temperature        
    vaporization change from liquid state to gaseous state        
    critical point temperature and pressure above which a gas cannot be condensed into a liquid        
    phase diagram pressure-temperature graph summarizing conditions under which the phases of a substance can exist        
    supercritical fluid substance at a temperature and pressure higher than its critical point; exhibits properties intermediate between those of gaseous and liquid states        
    triple point temperature and pressure at which the vapor, liquid, and solid phases of a substance are in equilibrium        
    amorphous solid (also, noncrystalline solid) solid in which the particles lack an ordered internal structure        
    covalent network solid solid whose particles are held together by covalent bonds        
    crystalline solid solid in which the particles are arranged in a definite repeating pattern        
    interstitial sites spaces between the regular particle positions in any array of atoms or ions        
    ionic solid solid composed of positive and negative ions held together by strong electrostatic attractions        
    metallic solid solid composed of metal atoms        
    molecular solid solid composed of neutral molecules held together by intermolecular forces of attraction        
    vacancy defect that occurs when a position that should contain an atom or ion is vacant        
    body-centered cubic (BCC) solid crystalline structure that has a cubic unit cell with lattice points at the corners and in the center of the cell        
    body-centered cubic unit cell simplest repeating unit of a body-centered cubic crystal; it is a cube containing lattice points at each corner and in the center of the cube        
    Bragg equation equation that relates the angles at which X-rays are diffracted by the atoms within a crystal        
    coordination number number of atoms closest to any given atom in a crystal or to the central metal atom in a complex        
    cubic closest packing (CCP) crystalline structure in which planes of closely packed atoms or ions are stacked as a series of three alternating layers of different relative orientations (ABC)        
    diffraction redirection of electromagnetic radiation that occurs when it encounters a physical barrier of appropriate dimensions        
    face-centered cubic (FCC) solid crystalline structure consisting of a cubic unit cell with lattice points on the corners and in the center of each face        
    face-centered cubic unit cell simplest repeating unit of a face-centered cubic crystal; it is a cube containing lattice points at each corner and in the center of each face        
    hexagonal closest packing (HCP) crystalline structure in which close packed layers of atoms or ions are stacked as a series of two alternating layers of different relative orientations (AB)        
    hole (also, interstice) space between atoms within a crystal        
    isomorphous possessing the same crystalline structure        
    octahedral hole open space in a crystal at the center of six particles located at the corners of an octahedron        
    simple cubic unit cell (also, primitive cubic unit cell) unit cell in the simple cubic structure        
    simple cubic structure crystalline structure with a cubic unit cell with lattice points only at the corners        
    space lattice all points within a crystal that have identical environments        
    tetrahedral hole tetrahedral space formed by four atoms or ions in a crystal        
    unit cell smallest portion of a space lattice that is repeated in three dimensions to form the entire lattice        
    X-ray crystallography experimental technique for determining distances between atoms in a crystal by measuring the angles at which X-rays are diffracted when passing through the crystal        
    alloy solid mixture of a metallic element and one or more additional elements        
    ideal solution solution that forms with no accompanying energy change        
    solvation exothermic process in which intermolecular attractive forces between the solute and solvent in a solution are established        
    spontaneous process physical or chemical change that occurs without the addition of energy from an external source        
    dissociation physical process accompanying the dissolution of an ionic compound in which the compound’s constituent ions are solvated and dispersed throughout the solution        
    electrolyte substance that produces ions when dissolved in water        
    ion-dipole attraction electrostatic attraction between an ion and a polar molecule        
    nonelectrolyte substance that does not produce ions when dissolved in water        
    strong electrolyte substance that dissociates or ionizes completely when dissolved in water        
    weak electrolyte substance that ionizes only partially when dissolved in water        
    Henry’s law law stating the proportional relationship between the concentration of dissolved gas in a solution and the partial pressure of the gas in contact with the solution        
    immiscible of negligible mutual solubility; typically refers to liquid substances        
    miscible mutually soluble in all proportions; typically refers to liquid substances        
    partially miscible of moderate mutual solubility; typically refers to liquid substances        
    saturated of concentration equal to solubility; containing the maximum concentration of solute possible for a given temperature and pressure        
    solubility extent to which a solute may be dissolved in water, or any solvent        
    supersaturated of concentration that exceeds solubility; a nonequilibrium state        
    unsaturated of concentration less than solubility        
    boiling point elevation elevation of the boiling point of a liquid by addition of a solute        
    boiling point elevation constant the proportionality constant in the equation relating boiling point elevation to solute molality; also known as the ebullioscopic constant        
    colligative property property of a solution that depends only on the concentration of a solute species        
    crenation process whereby biological cells become shriveled due to loss of water by osmosis        
    freezing point depression lowering of the freezing point of a liquid by addition of a solute        
    freezing point depression constant (also, cryoscopic constant) proportionality constant in the equation relating freezing point depression to solute molality        
    hemolysis rupture of red blood cells due to the accumulation of excess water by osmosis        
    hypertonic of greater osmotic pressure        
    hypotonic of less osmotic pressure        
    ion pair solvated anion/cation pair held together by moderate electrostatic attraction        
    isotonic of equal osmotic pressure        
    molality (m) a concentration unit defined as the ratio of the numbers of moles of solute to the mass of the solvent in kilograms        
    osmosis diffusion of solvent molecules through a semipermeable membrane        
    osmotic pressure (Π) opposing pressure required to prevent bulk transfer of solvent molecules through a semipermeable membrane        
    Raoult’s law the partial pressure exerted by a solution component is equal to the product of the component’s mole fraction in the solution and its equilibrium vapor pressure in the pure state        
    semipermeable membrane a membrane that selectively permits passage of certain ions or molecules        
    van’t Hoff factor (i) the ratio of the number of moles of particles in a solution to the number of moles of formula units dissolved in the solution        
    amphiphilic molecules possessing both hydrophobic (nonpolar) and a hydrophilic (polar) parts        
    colloid (also, colloidal dispersion) mixture in which relatively large solid or liquid particles are dispersed uniformly throughout a gas, liquid, or solid        
    dispersion medium solid, liquid, or gas in which colloidal particles are dispersed        
    dispersed phase substance present as relatively large solid or liquid particles in a colloid        
    emulsifying agent amphiphilic substance used to stabilize the particles of some emulsions        
    emulsion colloid formed from immiscible liquids        
    gel colloidal dispersion of a liquid in a solid        
    Tyndall effect scattering of visible light by a colloidal dispersion        
    average rate rate of a chemical reaction computed as the ratio of a measured change in amount or concentration of substance to the time interval over which the change occurred        
    initial rate instantaneous rate of a chemical reaction at t = 0 s (immediately after the reaction has begun)        
    instantaneous rate rate of a chemical reaction at any instant in time, determined by the slope of the line tangential to a graph of concentration as a function of time        
    rate of reaction measure of the speed at which a chemical reaction takes place        
    rate expression mathematical representation relating reaction rate to changes in amount, concentration, or pressure of reactant or product species per unit time        
    catalyst substance that increases the rate of a reaction without itself being consumed by the reaction        
    method of initial rates use of a more explicit algebraic method to determine the orders in a rate law        
    overall reaction order sum of the reaction orders for each substance represented in the rate law        
    rate constant (k) proportionality constant in the relationship between reaction rate and concentrations of reactants        
    rate law (also, rate equation) mathematical equation showing the dependence of reaction rate on the rate constant and the concentration of one or more reactants        
    reaction order value of an exponent in a rate law, expressed as an ordinal number (for example, zero order for 0, first order for 1, second order for 2, and so on)        
    half-life of a reaction (tl/2) time required for half of a given amount of reactant to be consumed        
    integrated rate law equation that relates the concentration of a reactant to elapsed time of reaction        
    activated complex (also, transition state) unstable combination of reactant species representing the highest energy state of a reaction system        
    activation energy (Ea) energy necessary in order for a reaction to take place        
    Arrhenius equation mathematical relationship between the rate constant and the activation energy of a reaction        
    collision theory model that emphasizes the energy and orientation of molecular collisions to explain and predict reaction kinetics        
    frequency factor (A) proportionality constant in the Arrhenius equation, related to the relative number of collisions having an orientation capable of leading to product formation        
    heterogeneous catalyst catalyst present in a different phase from the reactants, furnishing a surface at which a reaction can occur        
    homogeneous catalyst catalyst present in the same phase as the reactants        
    equilibrium in chemical reactions, the state in which the conversion of reactants into products and the conversion of products back into reactants occur simultaneously at the same rate; state of balance        
    reversible reaction chemical reaction that can proceed in both the forward and reverse directions under given conditions        
    equilibrium constant (K) value of the reaction quotient for a system at equilibrium        
    heterogeneous equilibria equilibria between reactants and products in different phases        
    homogeneous equilibria equilibria within a single phase        
    Kc equilibrium constant for reactions based on concentrations of reactants and products        
    KP equilibrium constant for gas-phase reactions based on partial pressures of reactants and products        
    law of mass action when a reversible reaction has attained equilibrium at a given temperature, the reaction quotient remains constant        
    reaction quotient (Q) ratio of the product of molar concentrations (or pressures) of the products to that of the reactants, each concentration (or pressure) being raised to the power equal to the coefficient in the equation        
    Le Chatelier's principle when a chemical system at equilibrium is disturbed, it returns to equilibrium by counteracting the disturbance        
    position of equilibrium concentrations or partial pressures of components of a reaction at equilibrium (commonly used to describe conditions before a disturbance)        
    stress change to a reaction's conditions that may cause a shift in the equilibrium        
    acid ionization reaction involving the transfer of a proton from an acid to water, yielding hydronium ions and the conjugate base of the acid        
    amphiprotic species that may either gain or lose a proton in a reaction        
    amphoteric species that can act as either an acid or a base        
    autoionization reaction between identical species yielding ionic products; for water, this reaction involves transfer of protons to yield hydronium and hydroxide ions        
    base ionization reaction involving the transfer of a proton from water to a base, yielding hydroxide ions and the conjugate acid of the base        
    Brønsted-Lowry acid proton donor        
    Brønsted-Lowry base proton acceptor        
    conjugate acid substance formed when a base gains a proton        
    conjugate base substance formed when an acid loses a proton        
    ion-product constant for water (Kw) equilibrium constant for the autoionization of water        
    acidic describes a solution in which \(\ce{[H3O^{+}] > [OH^{−}]}\)        
    basic describes a solution in which [H3O+] < [OH]        
    neutral describes a solution in which [H3O+] = [OH]        
    pH logarithmic measure of the concentration of hydronium ions in a solution        
    pOH logarithmic measure of the concentration of hydroxide ions in a solution        
    acid ionization constant (Ka) equilibrium constant for the ionization of a weak acid        
    base ionization constant (Kb) equilibrium constant for the ionization of a weak base        
    leveling effect of water any acid stronger than \(\ce{H3O+}\), or any base stronger than OH will react with water to form \(\ce{H3O+}\), or OH, respectively; water acts as a base to make all strong acids appear equally strong, and it acts as an acid to make all strong bases appear equally strong        
    oxyacid compound containing a nonmetal and one or more hydroxyl groups        
    percent ionization ratio of the concentration of the ionized acid to the initial acid concentration, times 100        
    diprotic acid acid containing two ionizable hydrogen atoms per molecule. A diprotic acid ionizes in two steps        
    diprotic base base capable of accepting two protons. The protons are accepted in two steps        
    monoprotic acid acid containing one ionizable hydrogen atom per molecule        
    stepwise ionization process in which an acid is ionized by losing protons sequentially        
    triprotic acid acid that contains three ionizable hydrogen atoms per molecule; ionization of triprotic acids occurs in three steps        
    buffer capacity amount of an acid or base that can be added to a volume of a buffer solution before its pH changes significantly (usually by one pH unit)        
    buffer mixture of a weak acid or a weak base and the salt of its conjugate; the pH of a buffer resists change when small amounts of acid or base are added        
    Henderson-Hasselbalch equation equation used to calculate the pH of buffer solutions        
    acid-base indicator organic acid or base whose color changes depending on the pH of the solution it is in        
    color-change interval range in pH over which the color change of an indicator takes place        
    titration curve plot of the pH of a solution of acid or base versus the volume of base or acid added during a titration        
    common ion effect effect on equilibrium when a substance with an ion in common with the dissolved species is added to the solution; causes a decrease in the solubility of an ionic species, or a decrease in the ionization of a weak acid or base        
    molar solubility solubility of a compound expressed in units of moles per liter (mol/L)        
    selective precipitation process in which ions are separated using differences in their solubility with a given precipitating reagent        
    solubility product (Ksp) equilibrium constant for the dissolution of a slightly soluble electrolyte        
    multiple equilibrium system characterized by more than one state of balance between a slightly soluble ionic solid and an aqueous solution of ions working simultaneously        
    nonspontaneous process process that requires continual input of energy from an external source        
    spontaneous change process that takes place without a continuous input of energy from an external source        
    entropy (S) state function that is a measure of the matter and/or energy dispersal within a system, determined by the number of system microstates often described as a measure of the disorder of the system        
    microstate (W) possible configuration or arrangement of matter and energy within a system        
    reversible process process that takes place so slowly as to be capable of reversing direction in response to an infinitesimally small change in conditions; hypothetical construct that can only be approximated by real processes removed        
    second law of thermodynamics entropy of the universe increases for a spontaneous process        
    standard entropy (S°) entropy for a substance at 1 bar pressure; tabulated values are usually determined at 298.15 K and denoted \(S^\circ_{298}\)        
    standard entropy change (ΔS°) change in entropy for a reaction calculated using the standard entropies, usually at room temperature and denoted \(ΔS^\circ_{298}\)        
    third law of thermodynamics entropy of a perfect crystal at absolute zero (0 K) is zero        
    Gibbs free energy change (G) thermodynamic property defined in terms of system enthalpy and entropy; all spontaneous processes involve a decrease in G        
    standard free energy change (ΔG°) change in free energy for a process occurring under standard conditions (1 bar pressure for gases, 1 M concentration for solutions)        
    standard free energy of formation \( (ΔG^\circ_\ce{f})\) change in free energy accompanying the formation of one mole of substance from its elements in their standard states        
    circuit path taken by a current as it flows because of an electrical potential difference        
    current flow of electrical charge; the SI unit of charge is the coulomb (C) and current is measured in amperes \(\mathrm{\left(1\: A=1\:\dfrac{C}{s}\right)}\)        
    electrical potential energy per charge; in electrochemical systems, it depends on the way the charges are distributed within the system; the SI unit of electrical potential is the volt \(\mathrm{\left(1\: V=1\:\dfrac{J}{C}\right)}\)        
    half-reaction method method that produces a balanced overall oxidation-reduction reaction by splitting the reaction into an oxidation “half” and reduction “half,” balancing the two half-reactions, and then combining the oxidation half-reaction and reduction half-reaction in such a way that the number of electrons generated by the oxidation is exactly canceled by the number of electrons required by the reduction        
    oxidation half-reaction the “half” of an oxidation-reduction reaction involving oxidation; the half-reaction in which electrons appear as products; balanced when each atom type, as well as the charge, is balanced        
    reduction half-reaction the “half” of an oxidation-reduction reaction involving reduction; the half-reaction in which electrons appear as reactants; balanced when each atom type, as well as the charge, is balanced        
    active electrode electrode that participates in the oxidation-reduction reaction of an electrochemical cell; the mass of an active electrode changes during the oxidation-reduction reaction        
    anode electrode in an electrochemical cell at which oxidation occurs; information about the anode is recorded on the left side of the salt bridge in cell notation        
    cathode electrode in an electrochemical cell at which reduction occurs; information about the cathode is recorded on the right side of the salt bridge in cell notation        
    cell notation shorthand way to represent the reactions in an electrochemical cell        
    cell potential difference in electrical potential that arises when dissimilar metals are connected; the driving force for the flow of charge (current) in oxidation-reduction reactions        
    galvanic cell electrochemical cell that involves a spontaneous oxidation-reduction reaction; electrochemical cells with positive cell potentials; also called a voltaic cell        
    inert electrode electrode that allows current to flow, but that does not otherwise participate in the oxidation-reduction reaction in an electrochemical cell; the mass of an inert electrode does not change during the oxidation-reduction reaction; inert electrodes are often made of platinum or gold because these metals are chemically unreactive.        
    voltaic cell another name for a galvanic cell        
    standard cell potential \( (E^\circ_\ce{cell})\) the cell potential when all reactants and products are in their standard states (1 bar or 1 atm or gases; 1 M for solutes), usually at 298.15 K; can be calculated by subtracting the standard reduction potential for the half-reaction at the anode from the standard reduction potential for the half-reaction occurring at the cathode        
    standard hydrogen electrode (SHE) the electrode consists of hydrogen gas bubbling through hydrochloric acid over an inert platinum electrode whose reduction at standard conditions is assigned a value of 0 V; the reference point for standard reduction potentials        
    standard reduction potential (E°) the value of the reduction under standard conditions (1 bar or 1 atm for gases; 1 M for solutes) usually at 298.15 K; tabulated values used to calculate standard cell potentials        
    concentration cell galvanic cell in which the two half-cells are the same except for the concentration of the solutes; spontaneous when the overall reaction is the dilution of the solute        
    electrical work (wele) negative of total charge times the cell potential; equal to wmax for the system, and so equals the free energy change (ΔG)        
    Faraday’s constant (F) charge on 1 mol of electrons; F = 96,485 C/mol e        
    Nernst equation equation that relates the logarithm of the reaction quotient (Q) to nonstandard cell potentials; can be used to relate equilibrium constants to standard cell potentials        
    cathodic protection method of protecting metal by using a sacrificial anode and effectively making the metal that needs protecting the cathode, thus preventing its oxidation        
    corrosion degradation of metal through an electrochemical process        
    galvanized iron method for protecting iron by covering it with zinc, which will oxidize before the iron; zinc-plated iron        
    sacrificial anode more active, inexpensive metal used as the anode in cathodic protection; frequently made from magnesium or zinc        
    alkaline earth metal any of the metals (beryllium, magnesium, calcium, strontium, barium, and radium) occupying group 2 of the periodic table; they are reactive, divalent metals that form basic oxides        
    allotropes two or more forms of the same element, in the same physical state, with different chemical structures        
    bismuth heaviest member of group 15; a less reactive metal than other representative metals        
    metal (representative) atoms of the metallic elements of groups 1, 2, 12, 13, 14, 15, and 16, which form ionic compounds by losing electrons from their outer s or p orbitals        
    metalloid element that has properties that are between those of metals and nonmetals; these elements are typically semiconductors        
    passivation metals with a protective nonreactive film of oxide or other compound that creates a barrier for chemical reactions; physical or chemical removal of the passivating film allows the metals to demonstrate their expected chemical reactivity        
    representative element element where the s and p orbitals are filling        
    representative metal metal among the representative elements        
    chemical reduction method of preparing a representative metal using a reducing agent        
    Downs cell electrochemical cell used for the commercial preparation of metallic sodium (and chlorine) from molten sodium chloride        
    Hall–Héroult cell electrolysis apparatus used to isolate pure aluminum metal from a solution of alumina in molten cryolite        
    Pidgeon process chemical reduction process used to produce magnesium through the thermal reaction of magnesium oxide with silicon        
    amorphous solid material such as a glass that does not have a regular repeating component to its three-dimensional structure; a solid but not a crystal        
    borate compound containing boron-oxygen bonds, typically with clusters or chains as a part of the chemical structure        
    polymorph variation in crystalline structure that results in different physical properties for the resulting compound        
    silicate compound containing silicon-oxygen bonds, with silicate tetrahedra connected in rings, sheets, or three-dimensional networks, depending on the other elements involved in the formation of the compounds        
    acid anhydride compound that reacts with water to form an acid or acidic solution        
    disproportionation reaction chemical reaction where a single reactant is simultaneously reduced and oxidized; it is both the reducing agent and the oxidizing agent        
    Haber process main industrial process used to produce ammonia from nitrogen and hydrogen; involves the use of an iron catalyst and elevated temperatures and pressures        
    hydrogen halide binary compound formed between hydrogen and the halogens: HF, HCl, HBr, and  HI        
    hydrogenation addition of hydrogen (H2) to reduce a compound        
    bicarbonate anion salt of the hydrogen carbonate ion, \(\ce{HCO3-}\)        
    carbonate salt of the anion \(\ce{CO3^2-}\); often formed by the reaction of carbon dioxide with bases        
    hydrogen carbonate salt of carbonic acid, H2CO3 (containing the anion \(\ce{HCO3-}\)) in which one hydrogen atom has been replaced; an acid carbonate; also known as bicarbonate ion        
    nitrogen fixation formation of nitrogen compounds from molecular nitrogen        
    base anhydride metal oxide that behaves as a base towards acids        
    chlor-alkali process electrolysis process for the synthesis of chlorine and sodium hydroxide        
    hydrogen sulfate \(\ce{HSO4-}\) ion        
    hydrogen sulfite \(\ce{HSO3-}\) ion        
    hydroxide compound of a metal with the hydroxide ion OH or the group −OH        
    nitrate \(\ce{NO3-}\) ion; salt of nitric acid        
    Ostwald process industrial process used to convert ammonia into nitric acid        
    oxide binary compound of oxygen with another element or group, typically containing O2− ions or the group –O– or =O        
    ozone allotrope of oxygen; O3        
    peroxide molecule containing two oxygen atoms bonded together or as the anion, \(\ce{O2^2-}\)        
    photosynthesis process whereby light energy promotes the reaction of water and carbon dioxide to form carbohydrates and oxygen; this allows photosynthetic organisms to store energy        
    sulfate \(\ce{SO4^2-}\) ion        
    sulfite \(\ce{SO3^2-}\) ion        
    superoxide oxide containing the anion \(\ce{O2-}\)        
    Frasch process important in the mining of free sulfur from enormous underground deposits        
    halide compound containing an anion of a group 17 element in the 1− oxidation state (fluoride, F; chloride, Cl; bromide, Br; and iodide, I)        
    interhalogen compound formed from two or more different halogens        
    actinide series (also, actinoid series) actinium and the elements in the second row or the f-block, atomic numbers 89–103        
    coordination compound stable compound in which the central metal atom or ion acts as a Lewis acid and accepts one or more pairs of electrons        
    d-block element one of the elements in groups 3–11 with valence electrons in d orbitals        
    f-block element (also, inner transition element) one of the elements with atomic numbers 58–71 or 90–103 that have valence electrons in f orbitals; they are frequently shown offset below the periodic table        
    first transition series transition elements in the fourth period of the periodic table (first row of the d-block), atomic numbers 21–29        
    fourth transition series transition elements in the seventh period of the periodic table (fourth row of the d-block), atomic numbers 89 and 104–111        
    hydrometallurgy process in which a metal is separated from a mixture by first converting it into soluble ions, extracting the ions, and then reducing the ions to precipitate the pure metal        
    lanthanide series (also, lanthanoid series) lanthanum and the elements in the first row or the f-block, atomic numbers 57–71        
    platinum metals group of six transition metals consisting of ruthenium, osmium, rhodium, iridium, palladium, and platinum that tend to occur in the same minerals and demonstrate similar chemical properties        
    rare earth element collection of 17 elements including the lanthanides, scandium, and yttrium that often occur together and have similar chemical properties, making separation difficult        
    second transition series transition elements in the fifth period of the periodic table (second row of the d-block), atomic numbers 39–47        
    smelting process of extracting a pure metal from a molten ore        
    steel material made from iron by removing impurities in the iron and adding substances that produce alloys with properties suitable for specific uses        
    superconductor material that conducts electricity with no resistance        
    third transition series transition elements in the sixth period of the periodic table (third row of the d-block), atomic numbers 57 and 72–79        
    bidentate ligand ligand that coordinates to one central metal through coordinate bonds from two different atoms        
    central metal ion or atom to which one or more ligands is attached through coordinate covalent bonds        
    chelate complex formed from a polydentate ligand attached to a central metal        
    chelating ligand ligand that attaches to a central metal ion by bonds from two or more donor atoms        
    cis configuration configuration of a geometrical isomer in which two similar groups are on the same side of an imaginary reference line on the molecule        
    coordination compound substance consisting of atoms, molecules, or ions attached to a central atom through Lewis acid-base interactions        
    coordination number number of coordinate covalent bonds to the central metal atom in a complex or the number of closest contacts to an atom in a crystalline form        
    coordination sphere central metal atom or ion plus the attached ligands of a complex        
    donor atom atom in a ligand with a lone pair of electrons that forms a coordinate covalent bond to a central metal        
    ionization isomer (or coordination isomer) isomer in which an anionic ligand is replaced by the counter ion in the inner coordination sphere        
    ligand ion or neutral molecule attached to the central metal ion in a coordination compound        
    linkage isomer coordination compound that possesses a ligand that can bind to the transition metal in two different ways (CN vs. NC)        
    monodentate ligand that attaches to a central metal through just one coordinate covalent bond        
    optical isomer (also, enantiomer) molecule that is a nonsuperimposable mirror image with identical chemical and physical properties, except when it reacts with other optical isomers        
    polydentate ligand ligand that is attached to a central metal ion by bonds from two or more donor atoms, named with prefixes specifying how many donors are present (e.g., hexadentate = six coordinate bonds formed)        
    trans configuration configuration of a geometrical isomer in which two similar groups are on opposite sides of an imaginary reference line on the molecule        
    crystal field splitting (Δoct) difference in energy between the t2g and eg sets or t and e sets of orbitals        
    crystal field theory model that explains the energies of the orbitals in transition metals in terms of electrostatic interactions with the ligands but does not include metal ligand bonding        
    eg orbitals set of two d orbitals that are oriented on the Cartesian axes for coordination complexes; in octahedral complexes, they are higher in energy than the t2g orbitals        
    geometric isomers isomers that differ in the way in which atoms are oriented in space relative to each other, leading to different physical and chemical properties        
    high-spin complex complex in which the electrons maximize the total electron spin by singly populating all of the orbitals before pairing two electrons into the lower-energy orbitals        
    low-spin complex complex in which the electrons minimize the total electron spin by pairing in the lower-energy orbitals before populating the higher-energy orbitals        
    pairing energy (P) energy required to place two electrons with opposite spins into a single orbital        
    spectrochemical series ranking of ligands according to the magnitude of the crystal field splitting they induce        
    strong-field ligand ligand that causes larger crystal field splittings        
    t2g orbitals set of three d orbitals aligned between the Cartesian axes for coordination complexes; in octahedral complexes, they are lowered in energy compared to the eg orbitals according to CFT        
    weak-field ligand ligand that causes small crystal field splittings        
    addition reaction reaction in which a double carbon-carbon bond forms a single carbon-carbon bond by the addition of a reactant. Typical reaction for an alkene.        
    alkane molecule consisting of only carbon and hydrogen atoms connected by single (σ) bonds        
    alkene molecule consisting of carbon and hydrogen containing at least one carbon-carbon double bond        
    alkyl group substituent, consisting of an alkane missing one hydrogen atom, attached to a larger structure        
    alkyne molecule consisting of carbon and hydrogen containing at least one carbon-carbon triple bond        
    aromatic hydrocarbon cyclic molecule consisting of carbon and hydrogen with delocalized alternating carbon-carbon single and double bonds, resulting in enhanced stability        
    functional group part of an organic molecule that imparts a specific chemical reactivity to the molecule        
    organic compound natural or synthetic compound that contains carbon        
    saturated hydrocarbon molecule containing carbon and hydrogen that has only single bonds between carbon atoms        
    skeletal structure shorthand method of drawing organic molecules in which carbon atoms are represented by the ends of lines and bends in between lines, and hydrogen atoms attached to the carbon atoms are not shown (but are understood to be present by the context of the structure)        
    substituent branch or functional group that replaces hydrogen atoms in a larger hydrocarbon chain        
    substitution reaction reaction in which one atom replaces another in a molecule        
    alcohol organic compound with a hydroxyl group (–OH) bonded to a carbon atom        
    ether organic compound with an oxygen atom that is bonded to two carbon atoms        
    amine organic molecule in which a nitrogen atom is bonded to one or more alkyl group        
    amide organic molecule that features a nitrogen atom connected to the carbon atom in a carbonyl group        
    band of stability (also, belt of stability, zone of stability, or valley of stability) region of graph of number of protons versus number of neutrons containing stable (nonradioactive) nuclides        
    binding energy per nucleon total binding energy for the nucleus divided by the number of nucleons in the nucleus        
    electron volt (eV) measurement unit of nuclear binding energies, with 1 eV equaling the amount energy due to the moving an electron across an electric potential difference of 1 volt        
    magic number nuclei with specific numbers of nucleons that are within the band of stability        
    mass defect difference between the mass of an atom and the summed mass of its constituent subatomic particles (or the mass “lost” when nucleons are brought together to form a nucleus)        
    mass-energy equivalence equation Albert Einstein’s relationship showing that mass and energy are equivalent        
    nuclear binding energy energy lost when an atom’s nucleons are bound together (or the energy needed to break a nucleus into its constituent protons and neutrons)        
    nuclear chemistry study of the structure of atomic nuclei and processes that change nuclear structure        
    nucleon collective term for protons and neutrons in a nucleus        
    nuclide nucleus of a particular isotope        
    radioactivity phenomenon exhibited by an unstable nucleon that spontaneously undergoes change into a nucleon that is more stable; an unstable nucleon is said to be radioactive        
    radioisotope isotope that is unstable and undergoes conversion into a different, more stable isotope        
    strong nuclear force force of attraction between nucleons that holds a nucleus together        
    alpha particle (α or \(\ce{^4_2He}\) or \(\ce{^4_2α}\)) high-energy helium nucleus; a helium atom that has lost two electrons and contains two protons and two neutrons        
    antimatter particles with the same mass but opposite properties (such as charge) of ordinary particles        
    beta particle (\(β\) or \(\ce{^0_{-1}e}\) or \(\ce{^0_{-1}β}\)) high-energy electron        
    gamma ray (γ or \(\ce{^0_0γ}\)) short wavelength, high-energy electromagnetic radiation that exhibits wave-particle duality        
    nuclear reaction change to a nucleus resulting in changes in the atomic number, mass number, or energy state        
    positron (\(\ce{^0_{+1}β}\) or \(\ce{^0_{+1}e}\)) antiparticle to the electron; it has identical properties to an electron, except for having the opposite (positive) charge        
    alpha (α) decay loss of an alpha particle during radioactive decay        
    beta (β) decay breakdown of a neutron into a proton, which remains in the nucleus, and an electron, which is emitted as a beta particle        
    daughter nuclide nuclide produced by the radioactive decay of another nuclide; may be stable or may decay further        
    electron capture combination of a core electron with a proton to yield a neutron within the nucleus        
    gamma (γ) emission decay of an excited-state nuclide accompanied by emission of a gamma ray        
    half-life (t1/2) time required for half of the atoms in a radioactive sample to decay        
    parent nuclide unstable nuclide that changes spontaneously into another (daughter) nuclide        
    positron emission (also, β+ decay) conversion of a proton into a neutron, which remains in the nucleus, and a positron, which is emitted        
    radioactive decay spontaneous decay of an unstable nuclide into another nuclide        
    radioactive decay series chains of successive disintegrations (radioactive decays) that ultimately lead to a stable end-product        
    radiocarbon dating highly accurate means of dating objects 30,000–50,000 years old that were derived from once-living matter; achieved by calculating the ratio of \(\ce{^{14}_6C : ^{12}_6C}\) in the object vs. the ratio of \(\ce{^{14}_6C : ^{12}_6C}\) in the present-day atmosphere        
    radiometric dating use of radioisotopes and their properties to date the formation of objects such as archeological artifacts, formerly living organisms, or geological formations        
    chain reaction repeated fission caused when the neutrons released in fission bombard other atoms        
    containment system (also, shield) a three-part structure of materials that protects the exterior of a nuclear fission reactor and operating personnel from the high temperatures, pressures, and radiation levels inside the reactor        
    control rod material inserted into the fuel assembly that absorbs neutrons and can be raised or lowered to adjust the rate of a fission reaction        
    critical mass amount of fissionable material that will support a self-sustaining (nuclear fission) chain reaction        
    fissile (or fissionable) when a material is capable of sustaining a nuclear fission reaction        
    fission splitting of a heavier nucleus into two or more lighter nuclei, usually accompanied by the conversion of mass into large amounts of energy        
    fusion combination of very light nuclei into heavier nuclei, accompanied by the conversion of mass into large amounts of energy        
    fusion reactor nuclear reactor in which fusion reactions of light nuclei are controlled        
    nuclear fuel fissionable isotope present in sufficient quantities to provide a self-sustaining chain reaction in a nuclear reactor        
    nuclear moderator substance that slows neutrons to a speed low enough to cause fission        
    nuclear reactor environment that produces energy via nuclear fission in which the chain reaction is controlled and sustained without explosion        
    nuclear transmutation conversion of one nuclide into another nuclide        
    particle accelerator device that uses electric and magnetic fields to increase the kinetic energy of nuclei used in transmutation reactions        
    reactor coolant assembly used to carry the heat produced by fission in a reactor to an external boiler and turbine where it is transformed into electricity        
    subcritical mass amount of fissionable material that cannot sustain a chain reaction; less than a critical mass        
    supercritical mass amount of material in which there is an increasing rate of fission        
    transmutation reaction bombardment of one type of nuclei with other nuclei or neutrons        
    transuranium element element with an atomic number greater than 92; these elements do not occur in nature        
    chemotherapy similar to internal radiation therapy, but chemical rather than radioactive substances are introduced into the body to kill cancer cells        
    external beam radiation therapy radiation delivered by a machine outside the body        
    internal radiation therapy (also, brachytherapy) radiation from a radioactive substance introduced into the body to kill cancer cells        
    radiation therapy use of high-energy radiation to damage the DNA of cancer cells, which kills them or keeps them from dividing        
    radioactive tracer (also, radioactive label) radioisotope used to track or follow a substance by monitoring its radioactive emissions        
    becquerel (Bq) SI unit for rate of radioactive decay; 1 Bq = 1 disintegration/s        
    curie (Ci) larger unit for rate of radioactive decay frequently used in medicine; 1 Ci = 3.7 × 1010 disintegrations/s        
    Geiger counter instrument that detects and measures radiation via the ionization produced in a Geiger-Müller tube        
    gray (Gy) SI unit for measuring radiation dose; 1 Gy = 1 J absorbed/kg tissue        
    ionizing radiation radiation that can cause a molecule to lose an electron and form an ion        
    millicurie (mCi) larger unit for rate of radioactive decay frequently used in medicine; 1 Ci = 3.7 × 1010 disintegrations/s        
    nonionizing radiation radiation that speeds up the movement of atoms and molecules; it is equivalent to heating a sample, but is not energetic enough to cause the ionization of molecules        
    radiation absorbed dose (rad) SI unit for measuring radiation dose, frequently used in medical applications; 1 rad = 0.01 Gy        
    radiation dosimeter device that measures ionizing radiation and is used to determine personal radiation exposure        
    relative biological effectiveness (RBE) measure of the relative damage done by radiation        
    roentgen equivalent man (rem) unit for radiation damage, frequently used in medicine; 1 rem = 1 Sv        
    scintillation counter instrument that uses a scintillator—a material that emits light when excited by ionizing radiation—to detect and measure radiation        
    sievert (Sv) SI unit measuring tissue damage caused by radiation; takes into account energy and biological effects of radiation        
    • Was this article helpful?