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     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 Icon of DNA strand. The infamous double helix CC-BY-SA; Delmar Larsen
    Glossary Entries
    Word(s) Definition Image Caption Link Source
    abbreviated electron configuration An electron configuration that uses one of the noble gases to represent the core of electrons up to that element.        
    absolute zero The minimum possible temperature, labeled 0 K (zero kelvins).        
    acid An ionic compound of the H+ cation dissolved in water.        
    acid dissociation constant The equilibrium constant for the dissociation of a weak acid into ions.        
    acid salt An ionic compound whose aqueous solution is slightly acidic.        
    activity series A list of elements that will replace elements below them in single-replacement reactions.        
    actual yield The amount that is actually produced in a chemical reaction.        
    addition reaction The reaction of a halogen molecule across a C–C double or triple bond.        
    alkaline battery A type of dry cell that contains an alkaline (i.e., basic) moist paste, rather than an acidic paste.        
    alkynes An aliphatic hydrocarbon that contains a C–C triple bond.        
    alpha particle A type of radioactive emission equivalent to a helium nucleus.        
    amphiprotic A substance that can act as a proton donor or a proton acceptor.        
    angular momentum quantum number An index that affects the energy and the spatial distribution of an electron in an atom. Represented by ℓ.        
    Aromatic hydrocarbons A hydrocarbon that contains a benzene ring.        
    Arrhenius base A compound that increases the hydroxide ion concentration in aqueous solution.        
    atmosphere A unit of pressure equal to the average atmospheric pressure at sea level; defined as exactly 760 mmHg.        
    atom The smallest piece of an element that maintains the identity of that element.        
    atomic bomb A weapon that depends on a nuclear chain reaction to generate immense forces.        
    atomic mass The weighted average of the masses of the isotopes that compose an element.        
    atomic mass unit One-twelfth of the mass of a carbon-12 atom.        
    atomic number The number of protons in an atom.        
    atomic radius An indication of the size of the atom.        
    atomic symbol A one- or two-letter representation of the name of an element.        
    autoionization constant of water The product of the hydrogen ion and hydroxide ion concentrations.        
    autoionization of water Water molecules act as acids (proton donors) and bases (proton acceptors) with each other to a tiny extent in all aqueous solutions.        
    balanced A condition when the reactants and products of a chemical equation have the same number of atoms of all elements present.        
    base A compound that increases the amount of OH ions in an aqueous solution.        
    basic salt An ionic compound whose aqueous solution is slightly basic.        
    battery A portable voltaic cell that generates electricity to power devices for our convenience.        
    beta particle A type of radioactive emission equivalent to an electron.        
    boiling point elevation The increase of a solution’s boiling point because of the presence of solute.        
    boiling point elevation constant The constant that relates the molality concentration of a solution and its boiling point change.        
    bond energy The approximate amount of energy needed to bread a covalent bond.        
    Boyle’s law A gas law that relates pressure and volume at constant temperature and amount.        
    Brønsted-Lowry base Any species that can accept a proton from another molecule.        
    buffer A solution that resists dramatic changes in pH.        
    calorimetry The process of measuring enthalpy changes for chemical reactions.        
    capacity The amount of strong acid or base a buffer can counteract.        
    catalyst A substance that increases the speed of a reaction.        
    chain reaction An exponential growth in a phenomenon.        
    Charles’s law A gas law that relates volume and temperature at constant pressure and amount.        
    chemical bond The connection between two atoms in a molecule.        
    chemical change The process of demonstrating a chemical property.        
    chemical equilibrium The point at which forward and reverse chemical reactions balance each other’s progress.        
    chemical nomenclature A very specific system for naming compounds, in which unique substances get unique names.        
    Chemical properties A characteristic that describes how matter changes form in the presence of other matter.        
    chemistry The study of the interactions of matter with other matter and with energy.        

    The part of a number in scientific notation that is multiplied by a power of 10.


    A number in a chemical equation indicating more than one molecule of the substance.

    cohesion The tendency of a substance to interact with itself.        
    colligative properties A property of solutions related to the fraction that the solute particles occupy in the solution, not their identity.        
    combined gas law A gas law that combines pressure, volume, and temperature.        
    combustion reaction A chemical reaction in which a reactant combines with oxygen to produce oxides of all other elements as products.        
    complete ionic equation A chemical equation in which the dissolved ionic compounds are written as separated ions.        
    composition reaction A chemical reaction in which a single substance is produced from multiple reactants.        
    compound A combination of more than one element.        
    concentrated A solution with a lot of solute.        
    concentration The removal of solvent, which increases the concentration of the solute in the solution.        
    condensed structural formula A listing of the atoms bonded to each C atom in a chain.        
    conjugate acid-base pairs Two species whose formulas differ by only a hydrogen ion.        
    conversion factor A fraction that can be used to convert a quantity from one unit to another.        
    covalent bond A chemical bond formed by two atoms sharing electrons.        
    covalent network solids A crystalline solid composed of atoms of one or more elements that are covalently bonded together in a seemingly never-ending fashion.        
    crystalline solid A solid with a regular, repeating three-dimensional structure.        
    curie (Ci) A unit of radioactivity equal to 3.7×1010 decays/s.        
    Dalton’s law of partial pressures The total pressure of a gas mixture, Ptot, is equal to the sum of the partial pressures of the components, Pi.        
    daughter isotope The product left over from the parent isotope in a nuclear equation.        
    decomposition reaction A chemical reaction in which a single substance becomes more than one substance.        
    degrees The unit of temperature scales.        
    Density A physical property defined as a substance’s mass divided by its volume.        
    derived units A unit that is a product or a quotient of a fundamental unit.        
    dilution equation The mathematical formula for calculating new concentrations or volumes when a solution is diluted or concentrated.        
    dipole-dipole interactions An intermolecular force caused by molecules with a permanent dipole.        
    dispersion force An intermolecular force caused by the instantaneous position of an electron in a molecule.        
    dissociation The process of an ionic compound separating into ions when it dissolves.        
    double bond A covalent bond composed of two pairs of bonding electrons.        
    double-replacement reaction A chemical reaction in which parts of two ionic compounds are exchanged.        
    dry cell A modern battery that does not contain large amounts of aqueous solution.        
    dynamic equilibrium A situation in which a process still occurs but the opposite process also occurs at the same rate so that there is no net change in the system.        
    electrolysis The process of making a nonspontaneous redox reaction occur by forcing electricity into a cell.        
    electromagnetic spectrum The full span of the possible wavelengths, frequencies, and energies of light.        
    electron affinity (EA) The energy change when a gas-phase atom accepts an electron.        
    electron configuration The representation of the organization of electrons in shells and subshells in an atom.        
    electron groups A covalent bond of any type or a lone electron pair.        
    Electron-deficient molecules A molecule with less than eight electrons in the valence shell of an atom.        
    electronegativity A qualitative scale for judging how much atoms of any element attract electrons.        
    electroplating The deposition of a thin layer of metal on an object for protective or decorative purposes.        
    element A substance that cannot be broken down into simpler chemical substances by ordinary chemical means.        
    Energy The ability to do work.        
    enthalpy change The heat of a process at constant pressure; denoted ΔH.        
    enthalpy of formation The enthalpy change for a formation reaction; denoted ΔHf.        
    enthalpy of fusion (or heat of fusion) The amount of energy needed to change from a solid to a liquid or from a liquid to a solid.        
    enthalpy of sublimation The amount of energy needed to change from a solid to a gas or from a gas to a solid.        
    enthalpy of vaporization The amount of energy needed to change from a liquid to a gas or from a gas to a liquid.        
    equilibrium constant A numerical value that relates to the ratio of products and reactants at equilibrium.        
    equivalence point The point of the reaction when all the analyte has been reacted with the titrant.        
    exact number A number from a defined relationship that technically has an infinite number of significant figures.        
    exothermic A chemical reaction that has a negative change in enthalpy.        
    expanded valence shell molecules A molecule with more than eight electrons in the valence shell of an atom.        
    Experiments A test of the natural universe to see if a guess (hypothesis) is correct.        
    exponent The raised number to the right of a 10 indicating the number of factors of 10 in the original number.        
    f block The columns of the periodic table in which f subshells are being occupied.        
    Formation reactions A chemical reaction that forms one mole of a substance from its constituent elements in their standard states.        
    freezing point depression The decrease of a solution’s freezing point because of the presence of solute.        
    freezing point depression constant The constant that relates the molality concentration of a solution and its freezing point change.        
    frequency The number of cycles of light that pass a given point in one second.        
    fundamental units One of the seven basic units of SI used in science.        
    Fusion A nuclear process in which small nuclei are combined into larger nuclei, releasing energy.        
    gamma rays A type of radioactive emission that is a very energetic form of electromagnetic radiation.        
    Geiger counter An electrical device that detects radioactivity.        
    half reaction method The method of balancing redox reactions by writing and balancing the individual half reactions.        
    half-life The amount of time it takes for one-half of a radioactive isotope to decay.        
    Heat The transfer of energy from one body to another due to a difference in temperature.        
    Hess’s law When chemical equations are combined algebraically, their enthalpies can be combined in exactly the same way.        
    heterogeneous equilibrium An equilibrium in which more than one phase of reactants or products is present.        
    hydrogen bonding The very strong interaction between molecules due to H atoms being bonded to N, O, or F atoms.        
    hydrogenation reaction The reaction of hydrogen across a C–C double or triple bond, usually in the presence of a catalyst.        
    hydrolysis A reaction with water.        
    hydronium ion The actual chemical species that represents a hydrogen ion.        
    hypothesis An educated guess about how the natural universe works.        
    ideal gas A gas that exactly follows the statements of the kinetic theory.        
    ideal gas law A gas law that relates all four independent physical properties of a gas under any conditions.        
    indicator A substance whose color change indicates the equivalence point of a titration.        
    ionic bond The attraction between oppositely charged ions.        
    ionic compounds A compound formed from positive and negative ions.        
    ionic formulas The chemical formula for an ionic compound.        
    ionic solid A crystalline solid composed of ions.        
    Ionization energy (IE) The amount of energy required to remove an electron from an atom in the gas phase.        
    isolated system A system that does not allow a transfer of energy or matter into or out of the system.        
    isomers A molecule with the same molecular formula as another molecule but a different structure.        
    isothermal A process that does not change the temperature.        
    joule The SI unit of energy.        
    kelvin The fundamental unit of temperature in SI.        
    kinetic theory of gases The fundamental model that describes the physical properties of gases.        
    lattice energy The measured strength of ionic bonding.        
    law A specific statement that is thought to be never violated by the entire natural universe.        
    law of conservation of energy The total energy of an isolated system does not increase or decrease.        
    law of mass action The relationship of the amounts of reactants and products at equilibrium.        
    Le Chatelier’s principle If an equilibrium is stressed, then the reaction shifts to reduce the stress.        
    Lewis electron dot diagram A representation of the valence electrons of an atom that uses dots around the symbol of the element.        
    limiting reagent The reactant that runs out first.        
    line spectrum An image that contains only certain colors of light.        
    lone electron pairs A pair of electrons that does not make a covalent bond.        
    magnetic quantum number The index that determines the orientation of the electron’s spatial distribution. Represented by m.        
    mass number The sum of the number of protons and neutrons in a nucleus.        
    mass-mass calculations A calculation in which you start with a given mass of a substance and calculate the mass of another substance involved in the chemical equation.        
    Matter Anything that has mass and takes up space.        
    meniscus The curved surface a liquid makes as it approaches a solid barrier.        
    metallic solid A solid with the characteristic properties of a metal.        
    modern atomic theory The concept that atoms play a fundamental role in chemistry.        
    molality The number of moles of solute per kilogram of solvent.        
    molar masses The mass of 1 mol of a substance in grams.        
    molar volume The volume of exactly 1 mol of a gas; equal to 22.4 L at STP.        
    Molarity The number of moles of solute divided by the number of liters of solution.        
    mole The number of things equal to the number of atoms in exactly 12 g of carbon-12; equals 6.022×1023 things.        
    mole fraction The ratio of the number of moles of a component in a mixture divided by the total number of moles in the sample.        
    mole-mass calculation A calculation in which you start with a given number of moles of a substance and calculate the mass of another substance involved in the chemical equation, or vice versa.        
    mole-mole calculation A stoichiometry calculation when one starts with moles of one substance and convert to moles of another substance using the balanced chemical equation.        
    molecular formula A formal listing of what and how many atoms are in a molecule.        
    molecular mass The sum of the masses of the atoms in a molecule.        
    molecular solid A crystalline solid whose components are covalently bonded molecules.        
    molecules The smallest part of a substance that has the physical and chemical properties of that substance.        
    net ionic equation A chemical equation with the spectator ions removed.        
    neutral salt An ionic compound that does not affect the acidity of its aqueous solution.        
    neutralization reaction The reaction of an acid and a base to produce water and a salt.        
    neutron A subatomic particle with no charge.        
    nonpolar covalent bond The equal sharing of electrons in a covalent bond.        
    normal boiling point The characteristic temperature at which a liquid becomes a gas when the surrounding pressure is exactly 1 atm.        
    Nuclear energy The controlled harvesting of energy from fission reactions.        
    nuclear equation A chemical equation that emphasizes changes in atomic nuclei.        
    nuclear reactor An apparatus designed to carefully control the progress of a nuclear reaction and extract the resulting energy for useful purposes.        
    nucleus The center of an atom that contains protons and neutrons.        
    numerical prefixes A prefix used with a unit that refers to a multiple or fraction of a fundamental unit to make a more conveniently sized unit for a specific quantity.        
    octet rule The trend that atoms like to have eight electrons in their valence shell.        
    Odd-electron molecules A molecule with an odd number of electrons in the valence shell of an atom.        
    orbital The specific set of principal, angular momentum, and magnetic quantum numbers for an electron.        
    osmotic pressure The tendency of a solution to pass solvent through a semipermeable membrane due to concentration differences.        
    oxidation number A number assigned to an atom that helps keep track of the number of electrons on the atom.        
    oxidation numbers A number assigned to an atom that helps keep track of the number of electrons on the atom.        
    oxidation-reduction (or redox) reactions A chemical reaction that involves the transfer of electrons.        
    partial pressure The pressure that an individual gas in a mixture has.        
    parts per billion (ppb) Ratio of mass of solute to total mass of sample times 1,000,000,000.        
    Pauli exclusion principle No two electrons in an atom can have the same set of four quantum numbers.        
    percent yield Actual yield divided by theoretical yield times 100% to give a percentage between 0% and 100%.        
    percentage composition by mass Ratio of mass of solute to the total mass of a sample times 100.        
    periodic table A chart of all the elements.        
    periodic trends Variation of properties versus position on the periodic table.        
    pH The negative logarithm of the hydrogen ion concentration.        
    pH scale The range of values from 0 to 14 that describes the acidity or basicity of a solution.        
    photon The name of a wave of light acting as a particle.        
    physical change A change that occurs when a sample of matter changes one or more of its physical properties.        
    Physical properties A characteristic that describes matter as it exists.        
    Planck’s constant The proportionality constant between the frequency and the energy of light.        
    pOH The negative logarithm of the hydroxide ion concentration.        
    polar covalent bond The unequal sharing of electrons in a covalent bond.        
    polyatomic ions An ion that contains more than one atom.        
    precipitate A solid that falls out of solution in a precipitation reaction.        
    Pressure Force per unit area.        
    primary batteries A battery that cannot be recharged.        
    products A final substance in a chemical equation.        
    quantitative A description of a specific amount of something.        
    quantized When a quantity is restricted to having only certain values.        
    quantum mechanics The theory of electrons that treats them as a wave.        
    rad A unit of radioactive exposure equal to 0.01 J/g of tissue.        
    radioactive decay The spontaneous change of a nucleus from one element to another.        
    radioactivity Emanations of particles and radiation from atomic nuclei.        
    Raoult’s law The mathematical formula for calculating the vapor pressure of a solution.        
    rem A unit of radioactive exposure that includes a factor to account for the type of radioactivity.        
    salt Any ionic compound that is formed from a reaction between an acid and a base.        
    salt bridge A part of a voltaic cell that contains a solution of some ionic compound whose ions migrate to either side of the voltaic cell to maintain the charge balance.        
    saturated hydrocarbons A carbon compound with the maximum possible number of H atoms in its formula.        
    Science The process of knowing about the natural universe through observation and experiment.        
    Scientific notation An expression of a number using powers of 10.        
    secondary batteries A battery that can be recharged.        
    semimetals (or metalloids) An element that has properties of both metals and nonmetals.        
    semipermeable membrane A thin membrane that will pass certain small molecules but not others.        
    shell A term used to describe electrons with the same principal quantum number.        
    significant figures The limit of the number of places a measurement can be properly expressed with.        
    single bond A covalent bond composed of one pair of electrons.        
    single-replacement reaction A chemical reaction in which one element is substituted for another element in a compound.        
    solubility The maximum amount of a solute that can be dissolved in a given amount of a solvent.        
    solubility product constant The equilibrium constant for a compound normally considered insoluble.        
    solubility rules General statements that predict which ionic compounds dissolve and which do not.        
    solute The minor component of a solution.        
    solution Another name for a homogeneous mixture.        
    specific heat capacity The proportionality constant between heat, mass, and temperature change; also called specific heat.        
    spectator ions An ion that does nothing in the overall course of a chemical reaction.        
    spin quantum number The index that indicates one of two spin states for an electron. Represented by ms.        
    spontaneous fission (or fission) The breaking apart of an atomic nucleus into smaller nuclei.        
    Standard notation A straightforward expression of a number.        
    standard reduction potentials The voltage of a reduction half reaction relative to the hydrogen half reaction.        
    Standard temperature and pressure (STP) A set of benchmark conditions used to compare other properties of gases; about 1 atm for pressure and 273 K for temperature.        
    stoichiometry The relating of one chemical substance to another using a balanced chemical reaction.        
    subshell A term used to describe electrons in a shell that have the same angular momentum quantum number.        
    substance Matter that has the same physical and chemical properties throughout.        
    supersaturated A unstable solution with more than the normal maximum amount of solute in it.        
    Surface tension An effect caused by an imbalance of forces on the atoms at the surface of a liquid.        
    surrounding atoms An atom that makes covalent bonds to the central atom(s).        
    theoretical yield An amount that is theoretically produced as calculated using the balanced chemical reaction.        
    theory A general statement that explains a large number of observations.        
    thermochemical equation A chemical equation that includes an enthalpy change.        
    titration A chemical reaction performed quantitatively to determine the exact amount of a reagent.        
    torr Another name for a millimeter of mercury.        
    tracer A substance that can be used to follow the pathway of that substance through a structure.        
    triple bond A covalent bond composed of three pairs of bonding electrons.        
    unsaturated A solution with less than the maximum amount of solute dissolved in it.        
    valence shell The highest-numbered shell in an atom that contains electrons.        
    valence shell electron pair repulsion (VSEPR) The general concept that estimates the shape of a simple molecule.        
    van’t Hoff factor The number of particles each solute formula unit breaks apart into when it dissolves.        
    vapor Material in the gas phase due to evaporation.        
    vapor pressure The partial pressure exerted by evaporation of a liquid.        
    vapor pressure depression The decrease of a solution’s vapor pressure because of the presence of a solute.        
    voltage The tendency for electrons to go from one half cell to another.        
    voltaic (galvanic) cell An apparatus that allows for useful electrical work to be extracted from a redox reaction.        
    weak acid Any acid that is less than 100% dissociated into ions in aqueous solution.        
    weak base Any base that is less than 100% dissociated into ions in aqueous solution.