Glossary
- Page ID
- 381308
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(Eg. "Genetic, Hereditary, DNA ...") | (Eg. "Relating to genes or heredity") | ![]() |
The infamous double helix | https://bio.libretexts.org/ | CC-BY-SA; Delmar Larsen |
Word(s) |
Definition |
Image | Caption | Link | Source |
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Accuracy | how closely a measurement aligns with a correct value | ||||
Acid anhydride | compound that reacts with water to form an acid or acidic solution | ||||
Acid ionization | reaction involving the transfer of a proton from an acid to water, yielding hydronium ions and the conjugate base of the acid | ||||
Acid ionization constant (Ka) | equilibrium constant for the ionization of a weak acid | ||||
Acid-base indicator | organic acid or base whose color changes depending on the pH of the solution it is in | ||||
Acidic | describes a solution in which [H3O+] > [OH?] | ||||
Actinide | inner transition metal in the bottom of the bottom two rows of the periodic table | ||||
Actinide series | (also, actinoid series) actinium and the elements in the second row or the f-block, atomic numbers 89–103 | ||||
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 | ||||
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 | ||||
Actual yield | amount of product formed in a reaction | ||||
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. | ||||
Adhesive force | force of attraction between molecules of different chemical identities | ||||
Alcohol | organic compound with a hydroxyl group (–OH) bonded to a carbon atom | ||||
Alkali metal | element in group 1 | ||||
Alkaline earth metal | element in group 2 | ||||
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 | ||||
Alkane | molecule consisting of only carbon and hydrogen atoms connected by single (?) 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 | ||||
Allotropes | two or more forms of the same element, in the same physical state, with different chemical structures | ||||
Alloy | solid mixture of a metallic element and one or more additional elements | ||||
Alpha (?) decay | loss of an alpha particle during radioactive decay | ||||
Alpha particle | (? or He24He24 or ?24?24) high-energy helium nucleus; a helium atom that has lost two electrons and contains two protons and two neutrons | ||||
Alpha particle (? particle) | positively charged particle consisting of two protons and two neutrons | ||||
Amide | organic molecule that features a nitrogen atom connected to the carbon atom in a carbonyl group | ||||
Amine | organic molecule in which a nitrogen atom is bonded to one or more alkyl group | ||||
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 | ||||
Amorphous solid | (also, noncrystalline solid) solid in which the particles lack an ordered internal structure | ||||
Amphiphilic | molecules possessing both hydrophobic (nonpolar) and a hydrophilic (polar) parts | ||||
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 | ||||
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) | ||||
Analyte | chemical species of interest | ||||
Angular momentum quantum number (l) | quantum number distinguishing the different shapes of orbitals; it is also a measure of the orbital angular momentum | ||||
Anion | negatively charged atom or molecule (contains more electrons than protons) | ||||
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 | ||||
Antimatter | particles with the same mass but opposite properties (such as charge) of ordinary particles | ||||
Aqueous solution | solution for which water is the solvent | ||||
Aromatic hydrocarbon | cyclic molecule consisting of carbon and hydrogen with delocalized alternating carbon-carbon single and double bonds, resulting in enhanced stability | ||||
Arrhenius equation | mathematical relationship between the rate constant and the activation energy of a reaction | ||||
Atmosphere (atm) | unit of pressure; 1 atm = 101,325 Pa | ||||
Atom | smallest particle of an element that can enter into a chemical combination | ||||
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 112112 of the mass of a 12C atom | ||||
Atomic number (Z) | number of protons in the nucleus of an atom | ||||
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 | ||||
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 | ||||
Autoionization | reaction between identical species yielding ionic products; for water, this reaction involves transfer of protons to yield hydronium and hydroxide ions | ||||
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 | ||||
Avogadro’s number (NA) | experimentally determined value of the number of entities comprising 1 mole of substance, equal to 6.022 × 1023 mol?1 | ||||
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 | ||||
Balanced equation | chemical equation with equal numbers of atoms for each element in the reactant and product | ||||
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 | ||||
Bar | (bar or b) unit of pressure; 1 bar = 100,000 Pa | ||||
Barometer | device used to measure atmospheric pressure | ||||
Base anhydride | metal oxide that behaves as a base towards acids | ||||
Base ionization | reaction involving the transfer of a proton from water to a base, yielding hydroxide ions and the conjugate acid of the base | ||||
Base ionization constant (Kb) | equilibrium constant for the ionization of a weak base | ||||
Basic | describes a solution in which [H3O+] < [OH?] | ||||
Becquerel (Bq) | SI unit for rate of radioactive decay; 1 Bq = 1 disintegration/s | ||||
Beta (?) decay | breakdown of a neutron into a proton, which remains in the nucleus, and an electron, which is emitted as a beta particle | ||||
Beta particle | (?? or e?10e?10 or ??10??10) high-energy electron | ||||
Bicarbonate anion | salt of the hydrogen carbonate ion, HCO?3HCO3? | ||||
Bidentate ligand | ligand that coordinates to one central metal through coordinate bonds from two different 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. | ||||
Binding energy per nucleon | total binding energy for the nucleus divided by the number of nucleons in the nucleus | ||||
Bismuth | heaviest member of group 15; a less reactive metal than other representative metals | ||||
Blackbody | idealized perfect absorber of all incident electromagnetic radiation; such bodies emit electromagnetic radiation in characteristic continuous spectra called blackbody radiation | ||||
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 | ||||
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. | ||||
Boiling point | temperature at which the vapor pressure of a liquid equals the pressure of the gas above it | ||||
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 | ||||
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 | ||||
Bond angle | angle between any two covalent bonds that share a common atom | ||||
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 | ||||
Bond distance | (also, bond length) distance between the nuclei of two bonded atoms | ||||
Bond energy | (also, bond dissociation energy) energy required to break a covalent bond in a gaseous substance | ||||
Bond length | distance between the nuclei of two bonded atoms at which the lowest potential energy is achieved | ||||
Borate | compound containing boron-oxygen bonds, typically with clusters or chains as a part of the chemical structure | ||||
Born-Haber cycle | thermochemical cycle relating the various energetic steps involved in the formation of an ionic solid from the relevant elements | ||||
Bragg equation | equation that relates the angles at which X-rays are diffracted by the atoms within a crystal | ||||
Brønsted-Lowry acid | proton donor | ||||
Brønsted-Lowry base | proton acceptor | ||||
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 | ||||
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) | ||||
Buret | device used for the precise delivery of variable liquid volumes, such as in a titration analysis | ||||
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 | ||||
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 | ||||
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 | ||||
Carbonate | salt of the anion CO2?3CO32?; often formed by the reaction of carbon dioxide with bases | ||||
Catalyst | substance that increases the rate of a reaction without itself being consumed by the reaction | ||||
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 | ||||
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 | ||||
Cation | positively charged atom or molecule (contains fewer electrons than protons) | ||||
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 | ||||
Celsius (°C) | unit of temperature; water freezes at 0 °C and boils at 100 °C on this scale | ||||
Central metal | ion or atom to which one or more ligands is attached through coordinate covalent bonds | ||||
Chain reaction | repeated fission caused when the neutrons released in fission bombard other atoms | ||||
Chalcogen | element in group 16 | ||||
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 | ||||
Chemical change | change producing a different kind of matter from the original kind of matter | ||||
Chemical equation | symbolic representation of a chemical reaction | ||||
Chemical property | behavior that is related to the change of one kind of matter into another kind of matter | ||||
Chemical reduction | method of preparing a representative metal using a reducing agent | ||||
Chemical symbol | one-, two-, or three-letter abbreviation used to represent an element or its atoms | ||||
Chemical thermodynamics | area of science that deals with the relationships between heat, work, and all forms of energy associated with chemical and physical processes | ||||
Chemistry | study of the composition, properties, and interactions of matter | ||||
Chemotherapy | similar to internal radiation therapy, but chemical rather than radioactive substances are introduced into the body to kill cancer cells | ||||
Chlor-alkali process | electrolysis process for the synthesis of chlorine and sodium hydroxide | ||||
Circuit | path taken by a current as it flows because of an electrical potential difference | ||||
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 | ||||
Clausius-Clapeyron equation | mathematical relationship between the temperature, vapor pressure, and enthalpy of vaporization for a substance | ||||
Coefficient | number placed in front of symbols or formulas in a chemical equation to indicate their relative amount | ||||
Cohesive force | force of attraction between identical molecules | ||||
Colligative property | property of a solution that depends only on the concentration of a solute species | ||||
Collision theory | model that emphasizes the energy and orientation of molecular collisions to explain and predict reaction kinetics | ||||
Colloid | (also, colloidal dispersion) mixture in which relatively large solid or liquid particles are dispersed uniformly throughout a gas, liquid, or solid | ||||
Color-change interval | range in pH over which the color change of an indicator takes place | ||||
Combustion analysis | gravimetric technique used to determine the elemental composition of a compound via the collection and weighing of its gaseous combustion products | ||||
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 | ||||
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 | ||||
Compound | pure substance that can be decomposed into two or more elements | ||||
Compressibility factor (Z) | ratio of the experimentally measured molar volume for a gas to its molar volume as computed from the ideal gas equation | ||||
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 | ||||
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 | ||||
Condensation | change from a gaseous to a liquid state | ||||
Conjugate acid | substance formed when a base gains a proton | ||||
Conjugate base | substance formed when an acid loses a proton | ||||
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 | ||||
Continuous spectrum | electromagnetic radiation given off in an unbroken series of wavelengths (e.g., white light from the sun) | ||||
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 | ||||
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 | ||||
Coordination compound | substance consisting of atoms, molecules, or ions attached to a central atom through Lewis acid-base interactions | ||||
Coordination number | number of atoms closest to any given atom in a crystal or to the central metal atom in a complex | ||||
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 | ||||
Core electron | electron in an atom that occupies the orbitals of the inner shells | ||||
Corrosion | degradation of metal through an electrochemical process | ||||
Covalent bond | attractive force between the nuclei of a molecule’s atoms and pairs of electrons between the atoms | ||||
Covalent bond | bond formed when electrons are shared between atoms | ||||
Covalent compound | (also, molecular compound) composed of molecules formed by atoms of two or more different elements | ||||
Covalent network solid | solid whose particles are held together by covalent bonds | ||||
Covalent radius | one-half the distance between the nuclei of two identical atoms when they are joined by a covalent bond | ||||
Crenation | process whereby biological cells become shriveled due to loss of water by osmosis | ||||
Critical mass | amount of fissionable material that will support a self-sustaining (nuclear fission) chain reaction | ||||
Critical point | temperature and pressure above which a gas cannot be condensed into a liquid | ||||
Crystal field splitting (?oct) | 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 | ||||
Crystalline solid | solid in which the particles are arranged in a definite repeating pattern | ||||
Cubic centimeter (cm3 or cc) | volume of a cube with an edge length of exactly 1 cm | ||||
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) | ||||
Cubic meter (m3) | SI unit of volume | ||||
Curie (Ci) | larger unit for rate of radioactive decay frequently used in medicine; 1 Ci = 3.7 × 1010 disintegrations/s | ||||
Current | flow of electrical charge; the SI unit of charge is the coulomb (C) and current is measured in amperes (1A=1Cs)(1A=1Cs) | ||||
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 | ||||
d-block element | one of the elements in groups 3–11 with valence electrons in d orbitals | ||||
Dalton (Da) | alternative unit equivalent to the atomic mass unit | ||||
Dalton’s atomic theory | set of postulates that established the fundamental properties of atoms | ||||
Daughter nuclide | nuclide produced by the radioactive decay of another nuclide; may be stable or may decay further | ||||
Density | ratio of mass to volume for a substance or object | ||||
Deposition | change from a gaseous state directly to a solid state | ||||
Diffraction | redirection of electromagnetic radiation that occurs when it encounters a physical barrier of appropriate dimensions | ||||
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 | ||||
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 | ||||
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 | ||||
Dipole-dipole attraction | intermolecular attraction between two permanent dipoles | ||||
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 | ||||
Dispersed phase | substance present as relatively large solid or liquid particles in a colloid | ||||
Dispersion force | (also, London dispersion force) attraction between two rapidly fluctuating, temporary dipoles; significant only when particles are very close together | ||||
Dispersion medium | solid, liquid, or gas in which colloidal particles are dispersed | ||||
Disproportionation reaction | chemical reaction where a single reactant is simultaneously reduced and oxidized; it is both the reducing agent and the oxidizing agent | ||||
Dissociation | physical process accompanying the dissolution of an ionic compound in which the compound’s constituent ions are solvated and dispersed throughout the solution | ||||
Dissolved | describes the process by which solute components are dispersed in a solvent | ||||
Donor atom | atom in a ligand with a lone pair of electrons that forms a coordinate covalent bond to a central metal | ||||
Double bond | covalent bond in which two pairs of electrons are shared between two atoms | ||||
Downs cell | electrochemical cell used for the commercial preparation of metallic sodium (and chlorine) from molten sodium chloride | ||||
Dynamic equilibrium | state of a system in which reciprocal processes are occurring at equal rates | ||||
Effective nuclear charge | charge that leads to the Coulomb force exerted by the nucleus on an electron, calculated as the nuclear charge minus shielding | ||||
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 | ||||
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 (1V=1JC)(1V=1JC) | ||||
Electrical work (wele) | negative of total charge times the cell potential; equal to wmax for the system, and so equals the free energy change (?G) | ||||
Electrolyte | substance that produces ions when dissolved in water | ||||
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 | ||||
Electron | negatively charged, subatomic particle of relatively low mass located outside the nucleus | ||||
Electron affinity | energy required to add an electron to a gaseous atom to form an anion | ||||
Electron capture | combination of a core electron with a proton to yield a neutron within the nucleus | ||||
Electron configuration | electronic structure of an atom in its ground state given as a listing of the orbitals occupied by the electrons | ||||
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 ? | ||||
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 | ||||
Electron-pair geometry | arrangement around a central atom of all regions of electron density (bonds, lone pairs, or unpaired electrons) | ||||
Electronegativity | tendency of an atom to attract electrons in a bond to itself | ||||
Element | substance that is composed of a single type of atom; a substance that cannot be decomposed by a chemical change | ||||
Empirical formula | formula showing the composition of a compound given as the simplest whole-number ratio of atoms | ||||
Empirical formula mass | sum of average atomic masses for all atoms represented in an empirical formula | ||||
Emulsifying agent | amphiphilic substance used to stabilize the particles of some emulsions | ||||
Emulsion | colloid formed from immiscible liquids | ||||
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) | ||||
Endothermic process | chemical reaction or physical change that absorbs heat | ||||
Energy | capacity to supply heat or do work | ||||
Enthalpy (H) | sum of a system’s internal energy and the mathematical product of its pressure and volume | ||||
Enthalpy change (?H) | heat released or absorbed by a system under constant pressure during a chemical or physical process | ||||
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 | ||||
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 | ||||
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 | ||||
Equilibrium constant (K) | value of the reaction quotient for a system at equilibrium | ||||
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 | ||||
Ether | organic compound with an oxygen atom that is bonded to two carbon atoms | ||||
Exact number | number derived by counting or by definition | ||||
Excess reactant | reactant present in an amount greater than required by the reaction stoichiometry | ||||
Excited state | state having an energy greater than the ground-state energy | ||||
Exothermic process | chemical reaction or physical change that releases heat | ||||
Expansion work (pressure-volume work) | work done as a system expands or contracts against external pressure | ||||
Extensive property | property of a substance that depends on the amount of the substance | ||||
External beam radiation therapy | radiation delivered by a machine outside the body | ||||
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 | ||||
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 | ||||
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 | ||||
Fahrenheit | unit of temperature; water freezes at 32 °F and boils at 212 °F on this scale | ||||
Faraday’s constant (F) | charge on 1 mol of electrons; F = 96,485 C/mol e? | ||||
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 | ||||
First transition series | transition elements in the fourth period of the periodic table (first row of the d-block), atomic numbers 21–29 | ||||
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 | ||||
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) | ||||
Formula mass | sum of the average masses for all atoms represented in a chemical formula; for covalent compounds, this is also the molecular mass | ||||
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 | ||||
Frasch process | important in the mining of free sulfur from enormous underground deposits | ||||
Free radical | molecule that contains an odd number of electrons | ||||
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 | ||||
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 | ||||
Frequency (??) | number of wave cycles (peaks or troughs) that pass a specified point in space per unit time | ||||
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 | ||||
Functional group | part of an organic molecule that imparts a specific chemical reactivity to the molecule | ||||
Fundamental unit of charge | (also called the elementary charge) equals the magnitude of the charge of an electron (e) with e = 1.602 ×× 10?19 C | ||||
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 | ||||
Galvanic cell | electrochemical cell that involves a spontaneous oxidation-reduction reaction; electrochemical cells with positive cell potentials; also called a voltaic cell | ||||
Galvanized iron | method for protecting iron by covering it with zinc, which will oxidize before the iron; zinc-plated iron | ||||
Gamma (?) emission | decay of an excited-state nuclide accompanied by emission of a gamma ray | ||||
Gamma ray | (? or ?00?00) short wavelength, high-energy electromagnetic radiation that exhibits wave-particle duality | ||||
Gas | state in which matter has neither definite volume nor shape | ||||
Geiger counter | instrument that detects and measures radiation via the ionization produced in a Geiger-Müller tube | ||||
Gel | colloidal dispersion of a liquid in a solid | ||||
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 | ||||
Gibbs free energy change (G) | thermodynamic property defined in terms of system enthalpy and entropy; all spontaneous processes involve a decrease in G | ||||
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 | ||||
Gray (Gy) | SI unit for measuring radiation dose; 1 Gy = 1 J absorbed/kg tissue | ||||
Ground state | state in which the electrons in an atom, ion, or molecule have the lowest energy possible | ||||
Group | vertical column of the periodic table | ||||
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 | ||||
Half-life (t1/2) | time required for half of the atoms in a radioactive sample to decay | ||||
Half-life of a reaction (tl/2) | time required for half of a given amount of reactant to be consumed | ||||
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 | ||||
Halide | compound containing an anion of a group 17 element in the 1? oxidation state (fluoride, F?; chloride, Cl?; bromide, Br?; and iodide, I?) | ||||
Hall–Héroult cell | electrolysis apparatus used to isolate pure aluminum metal from a solution of alumina in molten cryolite | ||||
Halogen | element in group 17 | ||||
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) | ||||
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 | ||||
Hemolysis | rupture of red blood cells due to the accumulation of excess water by osmosis | ||||
Henderson-Hasselbalch equation | equation used to calculate the pH of buffer solutions | ||||
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 | ||||
Hertz (Hz) | the unit of frequency, which is the number of cycles per second, s?1 | ||||
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 | ||||
Heterogeneous catalyst | catalyst present in a different phase from the reactants, furnishing a surface at which a reaction can occur | ||||
Heterogeneous equilibria | equilibria between reactants and products in different phases | ||||
Heterogeneous mixture | combination of substances with a composition that varies from point to point | ||||
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) | ||||
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 | ||||
Hole | (also, interstice) space between atoms within a crystal | ||||
Homogeneous catalyst | catalyst present in the same phase as the reactants | ||||
Homogeneous equilibria | equilibria within a single phase | ||||
Homogeneous mixture | (also, solution) combination of substances with a composition that is uniform throughout | ||||
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 | ||||
Hydrocarbon | compound composed only of hydrogen and carbon; the major component of fossil fuels | ||||
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 | ||||
Hydrogen carbonate | salt of carbonic acid, H2CO3 (containing the anion HCO?3HCO3?) in which one hydrogen atom has been replaced; an acid carbonate; also known as bicarbonate ion | ||||
Hydrogen halide | binary compound formed between hydrogen and the halogens: HF, HCl, HBr, and HI | ||||
Hydrogen sulfate | HSO?4HSO4? ion | ||||
Hydrogen sulfite | HSO?3HSO3? ion | ||||
Hydrogenation | addition of hydrogen (H2) to reduce a compound | ||||
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 | ||||
Hydrostatic pressure | pressure exerted by a fluid due to gravity | ||||
Hydroxide | compound of a metal with the hydroxide ion OH? or the group ?OH | ||||
Hypertonic | of greater osmotic pressure | ||||
Hypervalent molecule | molecule containing at least one main group element that has more than eight electrons in its valence shell | ||||
Hypothesis | tentative explanation of observations that acts as a guide for gathering and checking information | ||||
Hypotonic | of less osmotic pressure | ||||
Ideal solution | solution that forms with no accompanying energy change | ||||
Immiscible | of negligible mutual solubility; typically refers to liquid substances | ||||
Indicator | substance added to the sample in a titration analysis to permit visual detection of the end point | ||||
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 | ||||
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. | ||||
Inert gas | (also, noble gas) element in group 18 | ||||
Inert pair effect | tendency of heavy atoms to form ions in which their valence s electrons are not lost | ||||
Initial rate | instantaneous rate of a chemical reaction at t = 0 s (immediately after the reaction has begun) | ||||
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 | ||||
Instantaneous dipole | temporary dipole that occurs for a brief moment in time when the electrons of an atom or molecule are distributed asymmetrically | ||||
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 | ||||
Integrated rate law | equation that relates the concentration of a reactant to elapsed time of reaction | ||||
Intensity | property of wave-propagated energy related to the amplitude of the wave, such as brightness of light or loudness of sound | ||||
Intensive property | property of a substance that is independent of the amount of the substance | ||||
Interference pattern | pattern typically consisting of alternating bright and dark fringes; it results from constructive and destructive interference of waves | ||||
Interhalogen | compound formed from two or more different halogens | ||||
Intermolecular force | noncovalent attractive force between atoms, molecules, and/or ions | ||||
Internal energy (U) | total of all possible kinds of energy present in a substance or substances | ||||
Internal radiation therapy | (also, brachytherapy) radiation from a radioactive substance introduced into the body to kill cancer cells | ||||
Interstitial sites | spaces between the regular particle positions in any array of atoms or ions | ||||
Ion | electrically charged atom or molecule (contains unequal numbers of protons and electrons) | ||||
Ion pair | solvated anion/cation pair held together by moderate electrostatic attraction | ||||
Ion-dipole attraction | electrostatic attraction between an ion and a polar molecule | ||||
Ion-product constant for water (Kw) | equilibrium constant for the autoionization of water | ||||
Ionic bond | electrostatic forces of attraction between the oppositely charged ions of an ionic compound | ||||
Ionic bond | strong electrostatic force of attraction between cations and anions in an ionic compound | ||||
Ionic compound | compound composed of cations and anions combined in ratios, yielding an electrically neutral substance | ||||
Ionic solid | solid composed of positive and negative ions held together by strong electrostatic attractions | ||||
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+) | ||||
Ionization isomer | (or coordination isomer) isomer in which an anionic ligand is replaced by the counter ion in the inner coordination sphere | ||||
Ionizing radiation | radiation that can cause a molecule to lose an electron and form an ion | ||||
Isoelectronic | group of ions or atoms that have identical electron configurations | ||||
Isomers | compounds with the same chemical formula but different structures | ||||
Isomorphous | possessing the same crystalline structure | ||||
Isotonic | of equal osmotic pressure | ||||
Isotopes | atoms that contain the same number of protons but different numbers of neutrons | ||||
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 | ||||
Kc | equilibrium constant for reactions based on concentrations of reactants and products | ||||
Kelvin (K) | SI unit of temperature; 273.15 K = 0 ºC | ||||
Kilogram (kg) | standard SI unit of mass; 1 kg = approximately 2.2 pounds | ||||
Kinetic energy | energy of a moving body, in joules, equal to 12mv212mv2 (where m = mass and v = velocity) | ||||
KP | equilibrium constant for gas-phase reactions based on partial pressures of reactants and products | ||||
Lanthanide | inner transition metal in the top of the bottom two rows of the periodic table | ||||
Lanthanide series | (also, lanthanoid series) lanthanum and the elements in the first row or the f-block, atomic numbers 57–71 | ||||
Lattice energy (?Hlattice) | energy required to separate one mole of an ionic solid into its component gaseous ions | ||||
Law | statement that summarizes a vast number of experimental observations, and describes or predicts some aspect of the natural world | ||||
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 | ||||
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 definite proportions | (also, law of constant composition) all samples of a pure compound contain the same elements in the same proportions by mass | ||||
Law of mass action | when a reversible reaction has attained equilibrium at a given temperature, the reaction quotient remains constant | ||||
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 | ||||
Le Chatelier's principle | when a chemical system at equilibrium is disturbed, it returns to equilibrium by counteracting the disturbance | ||||
Length | measure of one dimension of an object | ||||
Leveling effect of water | any acid stronger than H3O+H3O+, or any base stronger than OH? will react with water to form H3O+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 | ||||
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 | ||||
Ligand | ion or neutral molecule attached to the central metal ion in a coordination compound | ||||
Limiting reactant | reactant present in an amount lower than required by the reaction stoichiometry, thus limiting the amount of product generated | ||||
Line spectrum | electromagnetic radiation emitted at discrete wavelengths by a specific atom (or atoms) in an excited state | ||||
Linear | shape in which two outside groups are placed on opposite sides of a central atom | ||||
Linkage isomer | coordination compound that possesses a ligand that can bind to the transition metal in two different ways (CN? vs. NC?) | ||||
Liquid | state of matter that has a definite volume but indefinite shape | ||||
Liter (L) | (also, cubic decimeter) unit of volume; 1 L = 1,000 cm3 | ||||
Lone pair | two (a pair of) valence electrons that are not used to form a covalent bond | ||||
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 | ||||
Macroscopic domain | realm of everyday things that are large enough to sense directly by human sight and touch | ||||
Magic number | nuclei with specific numbers of nucleons that are within the band of stability | ||||
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 | ||||
Main-group element | (also, representative element) element in columns 1, 2, and 12–18 | ||||
Manometer | device used to measure the pressure of a gas trapped in a container | ||||
Mass | fundamental property indicating amount of matter | ||||
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 number (A) | sum of the numbers of neutrons and protons in the nucleus of an atom | ||||
Mass percentage | ratio of solute-to-solution mass expressed as a percentage | ||||
Mass-energy equivalence equation | Albert Einstein’s relationship showing that mass and energy are equivalent | ||||
Mass-volume percent | ratio of solute mass to solution volume, expressed as a percentage | ||||
Matter | anything that occupies space and has mass | ||||
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 | ||||
Metal | element that is shiny, malleable, good conductor of heat and electricity | ||||
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 | ||||
Metallic solid | solid composed of metal atoms | ||||
Metalloid | element that conducts heat and electricity moderately well, and possesses some properties of metals and some properties of nonmetals | ||||
Metalloid | element that has properties that are between those of metals and nonmetals; these elements are typically semiconductors | ||||
Meter (m) | standard metric and SI unit of length; 1 m = approximately 1.094 yards | ||||
Method of initial rates | use of a more explicit algebraic method to determine the orders in a rate law | ||||
Microscopic domain | realm of things that are much too small to be sensed directly | ||||
Microstate (W) | possible configuration or arrangement of matter and energy within a system | ||||
Millicurie (mCi) | larger unit for rate of radioactive decay frequently used in medicine; 1 Ci = 3.7 × 1010 disintegrations/s | ||||
Milliliter (mL) | 1/1,000 of a liter; equal to 1 cm3 | ||||
Miscible | mutually soluble in all proportions; typically refers to liquid substances | ||||
Mixture | matter that can be separated into its components by physical means | ||||
Molality (m) | a concentration unit defined as the ratio of the numbers of moles of solute to the mass of the solvent in kilograms | ||||
Molar mass | mass in grams of 1 mole of a substance | ||||
Molar solubility | solubility of a compound expressed in units of moles per liter (mol/L) | ||||
Molarity (M) | unit of concentration, defined as the number of moles of solute dissolved in 1 liter of solution | ||||
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 | ||||
Molecular compound | (also, covalent compound) composed of molecules formed by atoms of two or more different elements | ||||
Molecular equation | chemical equation in which all reactants and products are represented as neutral substances | ||||
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. | ||||
Molecular solid | solid composed of neutral molecules held together by intermolecular forces of attraction | ||||
Molecular structure | arrangement of atoms in a molecule or ion | ||||
Molecular structure | structure that includes only the placement of the atoms in the molecule | ||||
Molecule | bonded collection of two or more atoms of the same or different elements | ||||
Monatomic ion | ion composed of a single atom | ||||
Monodentate | ligand that attaches to a central metal through just one coordinate covalent bond | ||||
Monoprotic acid | acid containing one ionizable hydrogen atom per molecule | ||||
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 | ||||
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 | ||||
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) | ||||
Neutral | describes a solution in which [H3O+] = [OH?] | ||||
Neutron | uncharged, subatomic particle located in the nucleus | ||||
Nitrate | NO?3NO3? ion; salt of nitric acid | ||||
Nitrogen fixation | formation of nitrogen compounds from molecular nitrogen | ||||
Noble gas | (also, inert gas) element in group 18 | ||||
Node | any point of a standing wave with zero amplitude | ||||
Node | plane separating different lobes of orbitals, where the probability of finding an electron is zero | ||||
Nomenclature | system of rules for naming objects of interest | ||||
Nonelectrolyte | substance that does not produce ions when dissolved in water | ||||
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 | ||||
Nonmetal | element that appears dull, poor conductor of heat and electricity | ||||
Nonspontaneous process | process that requires continual input of energy from an external source | ||||
Normal boiling point | temperature at which a liquid’s vapor pressure equals 1 atm (760 torr) | ||||
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 | ||||
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 reaction | change to a nucleus resulting in changes in the atomic number, mass number, or energy state | ||||
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 | ||||
Nucleon | collective term for protons and neutrons in a nucleus | ||||
Nucleus | massive, positively charged center of an atom made up of protons and neutrons | ||||
Nuclide | nucleus of a particular isotope | ||||
Nutritional calorie (Calorie) | unit used for quantifying energy provided by digestion of foods, defined as 1000 cal or 1 kcal | ||||
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 | ||||
Octahedral hole | open space in a crystal at the center of six particles located at the corners of an octahedron | ||||
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 | ||||
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 | ||||
Orbital diagram | pictorial representation of the electron configuration showing each orbital as a box and each electron as an arrow | ||||
Organic compound | natural or synthetic compound that contains carbon | ||||
Osmosis | diffusion of solvent molecules through a semipermeable membrane | ||||
Osmotic pressure (?) | opposing pressure required to prevent bulk transfer of solvent molecules through a semipermeable membrane | ||||
Ostwald process | industrial process used to convert ammonia into nitric acid | ||||
Overall reaction order | sum of the reaction orders for each substance represented in the rate law | ||||
Overlap | coexistence of orbitals from two different atoms sharing the same region of space, leading to the formation of a covalent bond | ||||
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 | ||||
Oxide | binary compound of oxygen with another element or group, typically containing O2? ions or the group –O– or =O | ||||
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) | ||||
Oxyacid | compound containing a nonmetal and one or more hydroxyl groups | ||||
Oxyanion | polyatomic anion composed of a central atom bonded to oxygen atoms | ||||
Ozone | allotrope of oxygen; O3 | ||||
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 | ||||
Pairing energy (P) | energy required to place two electrons with opposite spins into a single orbital | ||||
Parent nuclide | unstable nuclide that changes spontaneously into another (daughter) nuclide | ||||
Partially miscible | of moderate mutual solubility; typically refers to liquid substances | ||||
Particle accelerator | device that uses electric and magnetic fields to increase the kinetic energy of nuclei used in transmutation reactions | ||||
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 | ||||
Pascal (Pa) | SI unit of pressure; 1 Pa = 1 N/m2 | ||||
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 | ||||
Pauli exclusion principle | specifies that no two electrons in an atom can have the same value for all four quantum numbers | ||||
Percent composition | percentage by mass of the various elements in a compound | ||||
Percent ionization | ratio of the concentration of the ionized acid to the initial acid concentration, times 100 | ||||
Percent yield | measure of the efficiency of a reaction, expressed as a percentage of the theoretical yield | ||||
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 | ||||
Peroxide | molecule containing two oxygen atoms bonded together or as the anion, O2?2O22? | ||||
PH | logarithmic measure of the concentration of hydronium ions in a solution | ||||
Phase diagram | pressure-temperature graph summarizing conditions under which the phases of a substance can exist | ||||
Photon | smallest possible packet of electromagnetic radiation, a particle of light | ||||
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 | ||||
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 | ||||
Pi bond (? bond) | covalent bond formed by side-by-side overlap of atomic orbitals; the electron density is found on opposite sides of the internuclear axis | ||||
Pidgeon process | chemical reduction process used to produce magnesium through the thermal reaction of magnesium oxide with silicon | ||||
Plasma | gaseous state of matter containing a large number of electrically charged atoms and/or molecules | ||||
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 | ||||
Pnictogen | element in group 15 | ||||
POH | logarithmic measure of the concentration of hydroxide ions in a solution | ||||
Polar covalent bond | covalent bond between atoms of different electronegativities; a covalent bond with a positive end and a negative end | ||||
Polar molecule | (also, dipole) molecule with an overall dipole moment | ||||
Polarizability | measure of the ability of a charge to distort a molecule’s charge distribution (electron cloud) | ||||
Polyatomic ion | ion composed of more than one atom | ||||
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) | ||||
Polymorph | variation in crystalline structure that results in different physical properties for the resulting compound | ||||
Position of equilibrium | concentrations or partial pressures of components of a reaction at equilibrium (commonly used to describe conditions before a disturbance) | ||||
Positron (?+10?+10 or e+10e+10) | antiparticle to the electron; it has identical properties to an electron, except for having the opposite (positive) charge | ||||
Positron emission | (also, ?+ decay) conversion of a proton into a neutron, which remains in the nucleus, and a positron, which is emitted | ||||
Potential energy | energy of a particle or system of particles derived from relative position, composition, or condition | ||||
Pounds per square inch (psi) | unit of pressure common in the US | ||||
Precision | how closely a measurement matches the same measurement when repeated | ||||
Pressure | force exerted per unit area | ||||
Principal quantum number (n) | quantum number specifying the shell an electron occupies in an atom | ||||
Product | substance formed by a chemical or physical change; shown on the right side of the arrow in a chemical equation | ||||
Proton | positively charged, subatomic particle located in the nucleus | ||||
Pure covalent bond | (also, nonpolar covalent bond) covalent bond between atoms of identical electronegativities | ||||
Pure substance | homogeneous substance that has a constant composition | ||||
Quantitative analysis | the determination of the amount or concentration of a substance in a sample | ||||
Quantization | occurring only in specific discrete values, not continuous | ||||
Quantum mechanics | field of study that includes quantization of energy, wave-particle duality, and the Heisenberg uncertainty principle to describe matter | ||||
Quantum number | integer number having only specific allowed values and used to characterize the arrangement of electrons in an atom | ||||
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 | ||||
Radiation therapy | use of high-energy radiation to damage the DNA of cancer cells, which kills them or keeps them from dividing | ||||
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 | ||||
Radioactive tracer | (also, radioactive label) radioisotope used to track or follow a substance by monitoring its radioactive emissions | ||||
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 | ||||
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 C614:C612C614:C612 in the object vs. the ratio of C614:C612C614:C612 in the present-day atmosphere | ||||
Radioisotope | isotope that is unstable and undergoes conversion into a different, more stable isotope | ||||
Radiometric dating | use of radioisotopes and their properties to date the formation of objects such as archeological artifacts, formerly living organisms, or geological formations | ||||
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 | ||||
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 | ||||
Rate constant (k) | proportionality constant in the relationship between reaction rate and concentrations of reactants | ||||
Rate expression | mathematical representation relating reaction rate to changes in amount, concentration, or pressure of reactant or product species per unit time | ||||
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 | ||||
Rate of reaction | measure of the speed at which a chemical reaction takes place | ||||
Reactant | substance undergoing a chemical or physical change; shown on the left side of the arrow in a chemical equation | ||||
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) | ||||
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 | ||||
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 | ||||
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 | ||||
Relative biological effectiveness (RBE) | measure of the relative damage done by radiation | ||||
Representative element | (also, main-group element) element in columns 1, 2, and 12–18 | ||||
Representative element | element where the s and p orbitals are filling | ||||
Representative metal | metal among the representative elements | ||||
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 | ||||
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 | ||||
Reversible reaction | chemical reaction that can proceed in both the forward and reverse directions under given conditions | ||||
Roentgen equivalent man (rem) | unit for radiation damage, frequently used in medicine; 1 rem = 1 Sv | ||||
Rounding | procedure used to ensure that calculated results properly reflect the uncertainty in the measurements used in the calculation | ||||
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 | ||||
Sacrificial anode | more active, inexpensive metal used as the anode in cathodic protection; frequently made from magnesium or zinc | ||||
Saturated | of concentration equal to solubility; containing the maximum concentration of solute possible for a given temperature and pressure | ||||
Saturated hydrocarbon | molecule containing carbon and hydrogen that has only single bonds between carbon atoms | ||||
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 | ||||
Scintillation counter | instrument that uses a scintillator—a material that emits light when excited by ionizing radiation—to detect and measure radiation | ||||
Second (s) | SI unit of time | ||||
Second law of thermodynamics | entropy of the universe increases for a spontaneous process | ||||
Second transition series | transition elements in the fifth period of the periodic table (second row of the d-block), atomic numbers 39–47 | ||||
Selective precipitation | process in which ions are separated using differences in their solubility with a given precipitating reagent | ||||
Semipermeable membrane | a membrane that selectively permits passage of certain ions or molecules | ||||
Series | (also, period) horizontal row of the period table | ||||
Shell | set of orbitals with the same principal quantum number, n | ||||
SI units (International System of Units) | standards fixed by international agreement in the International System of Units (Le Système International d’Unités) | ||||
Sievert (Sv) | SI unit measuring tissue damage caused by radiation; takes into account energy and biological effects of radiation | ||||
Sigma bond (? bond) | covalent bond formed by overlap of atomic orbitals along the internuclear axis | ||||
Significant figures | (also, significant digits) all of the measured digits in a determination, including the uncertain last digit | ||||
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 | ||||
Simple cubic structure | crystalline structure with a cubic unit cell with lattice points only at the corners | ||||
Simple cubic unit cell | (also, primitive cubic unit cell) unit cell in the simple cubic structure | ||||
Single bond | bond in which a single pair of electrons is shared between two 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) | ||||
Smelting | process of extracting a pure metal from a molten ore | ||||
Solid | state of matter that is rigid, has a definite shape, and has a fairly constant volume | ||||
Solubility | extent to which a solute may be dissolved in water, or any solvent | ||||
Solubility product (Ksp) | equilibrium constant for the dissolution of a slightly soluble electrolyte | ||||
Solute | solution component present in a concentration less than that of the solvent | ||||
Solvation | exothermic process in which intermolecular attractive forces between the solute and solvent in a solution are established | ||||
Solvent | solution component present in a concentration that is higher relative to other components | ||||
Space lattice | all points within a crystal that have identical environments | ||||
Spatial isomers | compounds in which the relative orientations of the atoms in space differ | ||||
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) | ||||
Spectator ion | ion that does not undergo a chemical or physical change during a reaction, but its presence is required to maintain charge neutrality | ||||
Spectrochemical series | ranking of ligands according to the magnitude of the crystal field splitting they induce | ||||
Spin quantum number (ms) | number specifying the electron spin direction, either +12+12 or ?12?12 | ||||
Spontaneous change | process that takes place without a continuous input of energy from an external source | ||||
Spontaneous process | physical or chemical change that occurs without the addition of energy from an external source | ||||
Standard cell potential (E?cell)(Ecell?) | 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 enthalpy of combustion (?H?c?Hc?) | heat released when one mole of a compound undergoes complete combustion under standard conditions | ||||
Standard enthalpy of formation (?H?f?Hf?) | 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 entropy (S°) | entropy for a substance at 1 bar pressure; tabulated values are usually determined at 298.15 K and denoted S?298S298? | ||||
Standard entropy change (?S°) | change in entropy for a reaction calculated using the standard entropies, usually at room temperature and denoted ?S?298?S298? | ||||
Standard free energy change (?G°) | 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 (?G?f)(?Gf?) | change in free energy accompanying the formation of one mole of substance from its elements in their standard states | ||||
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 | ||||
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 | ||||
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 | ||||
State function | property depending only on the state of a system, and not the path taken to reach that state | ||||
Steel | material made from iron by removing impurities in the iron and adding substances that produce alloys with properties suitable for specific uses | ||||
Stepwise ionization | process in which an acid is ionized by losing protons sequentially | ||||
Stress | change to a reaction's conditions that may cause a shift in the equilibrium | ||||
Strong electrolyte | substance that dissociates or ionizes completely when dissolved in water | ||||
Strong nuclear force | force of attraction between nucleons that holds a nucleus together | ||||
Strong-field ligand | ligand that causes larger crystal field splittings | ||||
Structural formula | shows the atoms in a molecule and how they are connected | ||||
Structural isomer | one of two substances that have the same molecular formula but different physical and chemical properties because their atoms are bonded differently | ||||
Subcritical mass | amount of fissionable material that cannot sustain a chain reaction; less than a critical mass | ||||
Sublimation | change from solid state directly to gaseous state | ||||
Subshell | set of orbitals in an atom with the same values of n and l | ||||
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 | ||||
Sulfate | SO2?4SO42? ion | ||||
Sulfite | SO2?3SO32? ion | ||||
Superconductor | material that conducts electricity with no resistance | ||||
Supercritical fluid | substance at a temperature and pressure higher than its critical point; exhibits properties intermediate between those of gaseous and liquid states | ||||
Supercritical mass | amount of material in which there is an increasing rate of fission | ||||
Superoxide | oxide containing the anion O?2O2? | ||||
Supersaturated | of concentration that exceeds solubility; a nonequilibrium state | ||||
Surface tension | energy required to increase the area, or length, of a liquid surface by a given amount | ||||
Surroundings | all matter other than the system being studied | ||||
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 | ||||
System | portion of matter undergoing a chemical or physical change being studied | ||||
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 | ||||
Temperature | intensive property of matter that is a quantitative measure of “hotness” and “coldness” | ||||
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 | ||||
Tetrahedral hole | tetrahedral space formed by four atoms or ions in a crystal | ||||
Theoretical yield | amount of product that may be produced from a given amount of reactant(s) according to the reaction stoichiometry | ||||
Theory | well-substantiated, comprehensive, testable explanation of a particular aspect of nature | ||||
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 | ||||
Third law of thermodynamics | entropy of a perfect crystal at absolute zero (0 K) is zero | ||||
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 | ||||
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 | ||||
Titration curve | plot of the pH of a solution of acid or base versus the volume of base or acid added during a titration | ||||
Torr | unit of pressure; 1torr=1760atm1torr=1760atm | ||||
trans configuration | configuration of a geometrical isomer in which two similar groups are on opposite sides of an imaginary reference line on the molecule | ||||
Transition metal | element in columns 3–11 | ||||
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 | ||||
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 | ||||
Triple bond | bond in which three pairs of electrons are shared between two atoms | ||||
Triple point | temperature and pressure at which the vapor, liquid, and solid phases of a substance are in equilibrium | ||||
Triprotic acid | acid that contains three ionizable hydrogen atoms per molecule; ionization of triprotic acids occurs in three steps | ||||
Tyndall effect | scattering of visible light by a colloidal dispersion | ||||
Uncertainty | estimate of amount by which measurement differs from true value | ||||
Unified atomic mass unit (u) | alternative unit equivalent to the atomic mass unit | ||||
Unit | standard of comparison for measurements | ||||
Unit cell | smallest portion of a space lattice that is repeated in three dimensions to form the entire lattice | ||||
Unit conversion factor | ratio of equivalent quantities expressed with different units; used to convert from one unit to a different unit | ||||
Unsaturated | of concentration less than solubility | ||||
Vacancy | defect that occurs when a position that should contain an atom or ion is vacant | ||||
Valence bond theory | description of bonding that involves atomic orbitals overlapping to form ? or ? bonds, within which pairs of electrons are shared | ||||
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 | ||||
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 | ||||
Van der Waals equation | modified version of the ideal gas equation containing additional terms to account for non-ideal gas behavior | ||||
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 | ||||
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 | ||||
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 | ||||
Vector | quantity having magnitude and direction | ||||
Viscosity | measure of a liquid’s resistance to flow | ||||
Voltaic cell | another name for a galvanic cell | ||||
Volume | amount of space occupied by an object | ||||
Volume percentage | ratio of solute-to-solution volume expressed as a percentage | ||||
Wave | oscillation that can transport energy from one point to another in space | ||||
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) | ||||
Wavefunction (?) | 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 | ||||
Wavelength (?) | distance between two consecutive peaks or troughs in a wave | ||||
Weak electrolyte | substance that ionizes only partially when dissolved in water | ||||
Weak-field ligand | ligand that causes small crystal field splittings | ||||
Weight | force that gravity exerts on an object | ||||
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 | ||||
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 |