Vocabulary

A

absolute temperature scale A temperature scale that uses the absolute zero of temperature as the lowest temperature. (5.3)

absolute zero Theoretically the lowest attainable temperature. (5.3)

acceptor impurity An impurity that can accept electrons from a semiconductor. (21.3)

accuracy The closeness of a measurement to the true value of the quantity that is measured. (1.4)

acid A substance that yields hydrogen ions (H+) when dissolved in water. (2.7)

acid ionization constant (Ka) The equilibrium constant for the acid ionization. (15.5)

actinoid series Elements that have incompletely filled 5f subshells or readily give rise to cations that have incompletely filled 5f subshells. (7.9)

activated complex The species temporarily formed by the reactant molecules as a result of the collision before they form the product. (13.4)

activation energy (Ea) The minimum amount of energy required to initiate a chemical reaction. (13.4)

activity series A summary of the results of many possible displacement reactions. (4.4)

actual yield The amount of product actually obtained in a reaction. (3.10)

addition reaction A reaction in which one molecule adds to another. (24.2)

adhesion Attraction between unlike molecules. (11.3)

alcohol An organic compound containing the hydroxyl group —OH. (24.4)

aldehydes Compounds with a carbonyl functional group and the general formula RCHO, where R is an H atom, an alkyl, or an aromatic group. (24.4)

aliphatic hydrocarbons Hydrocarbons that do not contain the benzene group or the benzene ring. (24.1)

alkali metals The Group 1A elements (Li, Na, K, Rb, Cs, and Fr). (2.4)

alkaline earth metals The Group 2A elements (Be, Mg, Ca, Sr, Ba, and Ra). (2.4)

alkanes Hydrocarbons having the general formula CnH2n+2, where n = 1, 2, . . . . (24.2)

alkenes Hydrocarbons that contain one or more carbon-carbon double bonds. They have the general formula CnH2n, where n = 2, 3, . . . . (24.2)

alkynes Hydrocarbons that contain one or more carbon-carbon triple bonds. They have the general formula CnH2n, where n = 2, 3, . . . . (24.2)

allotropes Two or more forms of the same element that differ significantly in chemical and physical properties. (2.6)

alloy A solid solution composed of two or more metals, or of a metal or metals with one or more nonmetals. (21.2)

alpha (α) rays Helium ions with a positive charge of +2. (2.2)

alpha decay A radioactive process in which an alpha particle is emitted from a nucleus. (19.2)

alpha particles See alpha rays.

amalgam An alloy of mercury with another metal or metals. (21.2)

amines Organic bases that have the functional group —NR2, where R may be H, an alkyl group, or an aromatic group. (24.4)

amino acids A compound that contains at least one amino group and at least one carboxyl group. (25.3)

amorphous solid A solid that lacks a regular three-dimensional arrangement of atoms or molecules. (11.7)

amphoteric oxide An oxide that exhibits both acidic and basic properties. (8.6)

amplitude The vertical distance from the middle of a wave to the peak or trough. (7.1)

anion An ion with a net negative charge. (2.5)

anode The electrode at which oxidation occurs. (18.2)

antibonding molecular orbital A molecular orbital that is of higher energy and lower stability than the atomic orbitals from which it was formed. (10.6)

aqueous solution A solution in which the solvent is water. (4.1)

aromatic hydrocarbon A hydrocarbon that contains one or more benzene rings. (24.1)

atmospheric pressure The pressure exerted by Earth’s atmosphere. (5.2)

atom The basic unit of an element that can enter into chemical combination. (2.2)

atom economy A measure of the overall efficiency of converting reactants into useful products. (3.10)

atomic mass The mass of an atom in atomic mass units. (3.1)

atomic mass unit (amu) A mass exactly equal to the mass of one carbon-12 atom. (3.1)

atomic number (Z) The number of protons in the nucleus of an atom. (2.3)

atomic orbital The wave function (Ψ) of an electron in an atom. (7.5)

atomic radius One-half the distance between the two nuclei in two adjacent atoms of the same element in a metal. For elements that exist as diatomic units, the atomic radius is one-half the distance between the nuclei of the two atoms in a particular molecule. (8.3)

Aufbau principle As protons are added one by one to the nucleus to build up the elements, electrons similarly are added to the atomic orbitals. (7.9)

Avogadro’s law At constant pressure and temperature, the volume of a gas is directly proportional to the number of moles of the gas present. (5.3)

Avogadro’s number (NA) 6.022 × 1023; the number of particles in a mole. (3.2)

B

band theory Delocalized electrons move freely through “bands” formed by overlapping molecular orbitals. (21.3)

barometer An instrument that measures atmospheric pressure. (5.2)

base A substance that yields hydroxide ions (OH+) when dissolved in water. (2.7)

base ionization constant (Kb) The equilibrium constant for the base ­ionization. (15.6)

battery A galvanic cell, or a series of combined galvanic cells, that can be used as a source of direct electric current at a constant voltage. (18.6)

beta (β) rays Electrons. (2.2)

beta particles See beta rays.

bimolecular reaction An elementary step that involves two molecules. (13.5)

binary compounds Compounds formed from just two elements. (2.7)

boiling point The temperature at which the vapor pressure of a liquid is equal to the external atmospheric pressure. (11.8)

boiling-point elevation (ΔTb) The boiling point of the solution (Tb) minus the boiling point of the pure solvent. (12.6)

bond enthalpy The enthalpy change required to break a bond in 1 mole of gaseous ­molecules. (9.10)

bond length The distance between the nuclei of two bonded atoms in a molecule. (9.4)

bond order The difference between the numbers of electrons in bonding molecular orbitals and antibonding molecular orbitals, divided by two. (10.7)

bonding molecular orbital A molecular orbital that is of lower energy and greater stability than the atomic orbitals from which it was formed. (10.6)

Born-Haber cycle The cycle that relates ­lattice energies of ionic compounds to ­ionization energies, electron affinities, heats of sublimation and formation, and bond enthalpies. (9.3)

boundary surface diagram Diagram of the region containing a substantial amount of the electron density (about 90 percent) in an orbital. (7.7)

Boyle’s law The volume of a fixed amount of gas maintained at constant temperature is inversely proportional to the gas ­pressure. (5.3)

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breeder reactor A nuclear reactor that produces more fissionable materials than it uses. (19.5)

Brønsted acid A substance capable of donating a proton. (4.3)

Brønsted base A substance capable of accepting a proton. (4.3)

buffer solution A solution of (a) a weak acid or base and (b) its salt; both components must be present. The solution has the ­ability to resist changes in pH upon the ­addition of small amounts of either acid or base. (16.2)

C

calorimetry The measurement of heat changes. (6.5)

carbides Ionic compounds containing the C4− ion. (22.3)

carboxylic acids Acids that contain the carboxyl group —COOH. (24.4)

catalyst A substance that increases the rate of a chemical reaction without itself being consumed. (13.6)

catenation The ability of the atoms of an element to form bonds with one another. (22.3)

cathode The electrode at which reduction occurs. (18.2)

cation An ion with a net positive charge. (2.5)

cell voltage Difference in electrical potential between the anode and the cathode of a galvanic cell. (18.2)

Charles’s and Gay-Lussac’s law The volume of a fixed amount of gas maintained at constant pressure is directly proportional to the absolute temperature of the gas. (5.3).

Charles’s law The volume of a fixed amount of gas maintained at constant pressure is directly proportional to the absolute temperature of the gas. (5.3)

chelating agent A substance that forms complex ions with metal ions in solution. (23.2)

chemical energy Energy stored within the structural units of chemical substances. (6.1)

chemical equation An equation that uses chemical symbols to show what happens during a chemical reaction. (3.7)

chemical equilibrium A state in which the rates of the forward and reverse reactions are equal. (14.1)

chemical formula An expression showing the chemical composition of a compound in terms of the symbols for the atoms of the elements involved. (2.6)

chemical kinetics The area of chemistry concerned with the speeds, or rates, at which chemical reactions occur. (13.1)

chemical property Any property of a ­substance that cannot be studied without converting the substance into some other substance. (1.9)

chemical reaction A process in which a ­substance (or substances) is changed into one or more new substances. (3.7)

chemistry The study of matter and the changes it undergoes. (1.1)

chiral Compounds or ions that are not superimposable with their mirror images. (23.3)

chlor-alkali process The production of chlorine gas by the electrolysis of aqueous NaCl solution. (22.6)

closed system A system that enables the exchange of energy (usually in the form of heat) but not mass with its ­surroundings. (6.2)

closest packing The most efficient arrangements for packing atoms, molecules, or ions in a crystal. (11.4)

cohesion The intermolecular attraction between like molecules. (11.3)

colligative properties Properties of solutions that depend on the number of solute particles in solution and not on the nature of the solute particles. (12.6)

colloid A dispersion of particles of one substance (the dispersed phase) throughout a dispersing medium made of another substance. (12.8)

combination reaction A reaction in which two or more substances combine to form a single product. (4.4)

combustion reaction A reaction in which a substance reacts with oxygen, usually with the release of heat and light, to produce a flame. (4.4)

common ion effect The shift in equilibrium caused by the addition of a compound having an ion in common with the dissolved substances. (16.1)

complex ion An ion containing a central metal cation bonded to one or more molecules or ions. (16.7)

compound A substance composed of atoms of two or more elements chemically united in fixed proportions. (1.7)

concentration of a solution The amount of solute present in a given quantity of solvent or solution. (4.5)

condensation The phenomenon of going from the gaseous state to the liquid state. (11.8)

condensation reaction A reaction in which two smaller molecules combine to form a larger molecule. Water is invariably one of the products of such a reaction. (24.4)

conductor Substance capable of conducting electric current. (21.3)

conjugate acid-base pair An acid and its conjugate base or a base and its conjugate acid. (15.1)

coordinate covalent bond A bond in which the pair of electrons is supplied by one of the two bonded atoms; also called a dative bond. (9.9)

coordination compound A neutral species containing one or more complex ions. (23.2)

coordination number In a crystal lattice it is defined as the number of atoms (or ions) surrounding an atom (or ion) (11.4). In coordination compounds it is defined as the number of donor atoms surrounding the central metal atom in a complex. (23.2)

copolymer A polymer containing two or more different monomers. (25.2)

core electrons All nonvalence electrons in an atom. (8.2)

corrosion The deterioration of metals by an electrochemical process. (18.7)

Coulomb’s law The potential energy between two ions is directly proportional to the product of their charges and inversely proportional to the distance between them. (9.3)

covalent bond A bond in which two electrons are shared by two atoms. (9.4)

covalent compounds Compounds containing only covalent bonds. (9.4)

critical mass The minimum mass of fissionable material required to generate a self-sustaining nuclear chain reaction. (19.5)

critical point A point on a phase diagram where a phase boundary ends. (11.9)

critical pressure (Pc) The minimum pressure necessary to bring about liquefaction at the critical temperature. (11.8)

critical temperature (Tc) The temperature above which a gas will not liquefy. (11.8)

crystal field splitting (Δ) The energy difference between two sets of d orbitals in a metal atom when ligands are present. (23.4)

crystalline solid A solid that possesses rigid and long-range order; its atoms, molecules, or ions occupy specific positions. (11.4)

crystallization The process in which dissolved solute comes out of solution and forms crystals. (12.1)

cyanides Compounds containing the CN− ion. (22.3)

cycloalkanes Alkanes whose carbon atoms are joined in rings. (24.2)

D

Dalton’s law of partial pressures The total pressure of a mixture of gases is just the sum of the pressures that each gas would exert if it were present alone. (5.6)

decomposition reaction The breakdown

of a compound into two or more ­components. (4.4)

degenerate orbitals Atomic orbitals with the same energy. (7.6)

delocalized molecular orbitals Molecular orbitals that are not confined between two adjacent bonding atoms but actually extend over three or more atoms. (10.8)

denatured protein Protein that does not exhibit normal biological activities. (25.3)

density The mass of a substance divided by its volume. (1.9)

deoxyribonucleic acid (DNA) A type of nucleic acid. (25.4)

deposition The process in which the molecules go directly from the vapor into the solid phase. (11.8)

diagonal relationship Similarities between pairs of elements in different groups and periods of the periodic table. (8.6)

diamagnetic Repelled by a magnet; a diamagnetic substance contains only paired electrons. (7.8)

diatomic molecule A molecule that consists of two atoms. (2.5)

diffusion The gradual mixing of molecules of one gas with the molecules of another by virtue of their kinetic properties. (5.7)

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dilution A procedure for preparing a less ­concentrated solution from a more ­concentrated solution. (4.5)

dipole moment (µ) The product of charge and the distance between the charges in a molecule. (10.2)

dipole-dipole forces Forces that act between polar molecules. (11.2)

diprotic acid Each unit of the acid yields two hydrogen ions upon ionization. (4.3)

dispersion forces The attractive forces that arise as a result of temporary dipoles induced in the atoms or molecules; also called London forces. (11.2)

displacement reaction An atom or an ion in a compound is replaced by an atom of another element. (4.4)

disproportionation reaction A reaction in which an element in one oxidation state is both oxidized and reduced. (4.4)

donor atom The atom in a ligand that is bonded directly to the metal atom. (23.2)

donor impurity An impurity that provides conduction electrons to a semiconductor. (21.3)

double bond Two atoms are held together by two pairs of electrons. (9.4)

dynamic equilibrium The condition in which the rate of a forward process is ­exactly balanced by the rate of a reverse process. (11.8)

E

effective nuclear charge (Zeff) The nuclear charge felt by an electron when both the actual charge (Z) and the repulsive effect (shielding) of the other electrons are taken into account. (8.3)

effusion A process by which a gas under pressure escapes from one compartment of a container to another by passing through a small opening. (5.7)

electrochemistry The branch of chemistry that deals with the interconversion of electrical energy and chemical energy. (18.1)

electrolysis A process in which electrical energy is used to cause a nonspontaneous chemical reaction to occur. (18.8)

electrolyte A substance that, when dissolved in water, results in a solution that can conduct electricity. (4.1)

electrolytic cell An apparatus for carrying out electrolysis. (18.8)

electromagnetic radiation The emission and transmission of energy in the form of electromagnetic waves. (7.1)

electromagnetic wave A wave that has an electric field component and a mutually perpendicular magnetic field ­component. (7.1)

electromotive force (emf) (E) The voltage difference between electrodes. (18.2)

electron A subatomic particle that has a very low mass and carries a single negative electric charge. (2.2)

electron affinity (EA) The negative of the ­enthalpy change when an electron is ­accepted by an atom in the gaseous state to form an anion. (8.5)

electron capture A type of radioactive decay in which a nucleus captures an orbital electron, usually a 1s electron. (19.2)

electron configuration The distribution of electrons among the various orbitals in an atom or molecule. (7.8)

electron density The probability that an electron will be found at a particular region in an atomic orbital. (7.5)

electronegativity The ability of an atom to attract electrons toward itself in a chemical bond. (9.5)

electrostatic energy Potential energy (measured in joules) that results from conservative coulomb forces and is associated with the configuration of a particular set of charges. (6.1)

element A substance that cannot be separated into simpler substances by chemical means. (1.7)

elementary steps A series of simple reactions that represent the progress of the overall reaction at the molecular level. (13.5)

emission spectra Continuous or line spectra emitted by substances. (7.3)

empirical formula An expression showing the types of elements present and the simplest ratios of the different kinds of atoms. (2.6)

enantiomers Optical isomers, that is, compounds and their nonsuperimposable mirror images. (23.3)

end point The pH at which the indicator changes color. (16.4)

endothermic processes Processes that absorb heat from the surroundings. (6.2)

energy The capacity to do work or to produce change. (6.1)

enthalpy (H) A thermodynamic quantity used to describe heat changes taking place at constant pressure. (6.4)

enthalpy of reaction (ΔHrxn) The difference between the enthalpies of the products and the enthalpies of the reactants. (6.4)

enthalpy of solution (ΔHsoln) The heat generated or absorbed when a certain amount of solute is dissolved in a certain amount of solvent. (6.7)

entropy (S) A measure of how dispersed the energy of a system is among the ­different ways that system can contain ­energy. (17.2)

enzyme A biological catalyst. (13.6)

equilibrium constant (K) A number equal to the ratio of the equilibrium concentrations of products to the equilibrium concentrations of reactants, each raised to the power of its stoichiometric coefficient. (14.1)

equilibrium vapor pressure The vapor pressure measured under dynamic equilibrium of condensation and evaporation at some temperature. (11.8)

equivalence point The point at which the acid has completely reacted with or been neutralized by the base. (4.7)

esters Compounds that have the general ­formula R′COOR, where R′ can be H or an alkyl group or an aromatic group and R is an alkyl group or an aromatic group. (24.4)

ether An organic compound containing the R—O—R′ linkage, where R and R′ are alkyl and/or aromatic groups. (24.4)

evaporation The process in which a liquid is transformed into a gas; also called ­vaporization. (11.8)

excess reactants One or more reactants present in quantities greater than necessary to react with the quantity of the limiting reagent. (3.9)

excited state (or level) A state that has higher energy than the ground state. (7.3)

exothermic processes Processes that give off heat to the surroundings. (6.2)

extensive property A property that depends on how much matter is being ­considered. (1.9)

F

family The elements in a vertical column of the periodic table. (2.4)

Faraday constant (F) Charge contained in 1 mole of electrons, equivalent to 96,485.3 coulombs. (18.4)

ferromagnetic Attracted by a magnet. The unpaired spins in a ferromagnetic ­substance are aligned in a common ­direction. (21.2)

first law of thermodynamics Energy can be converted from one form to another, but cannot be created or destroyed. (6.3)

first-order reaction A reaction whose rate depends on reactant concentration raised to the first power. (13.3)

formal charge The difference between the valence electrons in an isolated atom and the number of electrons assigned to that atom in a Lewis structure. (9.7)

formation constant (Kf) The equilibrium constant for the complex ion ­formation. (16.7)

fractional crystallization The separation of a mixture of substances into pure ­components on the basis of their different solubilities. (12.4)

fractional distillation A procedure for ­separating liquid components of a solution that is based on their different boiling points. (12.6)

free energy (G) See Gibbs energy.

freezing point The temperature at which the solid and liquid phases of a substance coexist at equilibrium. (11.8)

freezing-point depression (ΔTf) The freezing point of the pure solvent ­minus the freezing point of the solution (Tf). (12.6)

frequency (ν) The number of waves that pass through a particular point per unit time. (7.1)

fuel cell A galvanic cell that requires a ­continuous supply of reactants to keep functioning. (18.6)

functional group That part of a molecule characterized by a special arrangement of atoms that is largely responsible for the chemical behavior of the parent ­molecule. (24.1)

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G

galvanic cell The experimental apparatus for generating electricity through the use of a spontaneous redox reaction. (18.2)

gamma (γ) rays High-energy radiation. (2.2)

gamma emission The type of radioactive decay in which gamma rays are emitted from an excited nucleus. (19.2)

gas constant (R) The constant that appears in the ideal gas equation. It is usually expressed as 0.08206 L · atm/K · mol, or 8.314 J/K · mol. (5.4)

geometric isomers Compounds with the same type and number of atoms and the same chemical bonds but different spatial arrangements; such isomers cannot be interconverted without breaking a chemical bond. (23.3)

Gibbs energy The energy available to do useful work. (17.4)

glass The optically transparent fusion product of inorganic materials that has cooled to a rigid state without crystallizing. (11.7)

Graham’s law of diffusion Under the same conditions of temperature and pressure, rates of diffusion for gases are inversely proportional to the square roots of their molar masses. (5.7)

gravimetric analysis An experimental procedure that involves the measurement of mass. (4.6)

greenhouse effect Carbon dioxide and other gases’ influence on Earth’s ­temperature. (20.5)

ground state (or level) The lowest energy state of a system. (7.3)

group The elements in a vertical column of the periodic table. (2.4)

H

half-cell reactions Oxidation and reduction reactions at the electrodes. (18.2)

half-life (t½) The time required for the ­concentration of a reactant to decrease to half of its initial concentration. (13.3)

half-reaction A reaction that explicitly shows electrons involved in either oxidation or reduction. (4.4)

halogens The nonmetallic elements in Group 7A (F, Cl, Br, I, and At). (2.4)

heat Transfer of energy between two bodies that are at different temperatures. (6.2)

heat capacity (C) The amount of heat required to raise the temperature of a given quantity of the substance by one degree Celsius. (6.5)

heat of dilution The heat change associated with the dilution process. (6.7)

heat of hydration (ΔHhydr) The heat change associated with the hydration process. (6.7)

heat of solution See enthalpy of solution.

Heisenberg uncertainty principle It is impossible to know simultaneously both the momentum and the position of a particle with certainty. (7.5)

Henry’s law The solubility of a gas in a liquid is proportional to the pressure of the gas over the solution. (12.5)

Hess’s law When reactants are converted to products, the change in enthalpy is the same whether the reaction takes place in one step or in a series of steps. (6.6)

heterogeneous equilibrium An equilibrium state in which the reacting species are not all in the same phase. (14.2)

heterogeneous mixture The individual components of a mixture remain physically separated and can be seen as separate components. (1.7)

homogeneous equilibrium An equilibrium state in which all reacting species are in the same phase. (14.2)

homogeneous mixture The composition of a mixture, after sufficient stirring, is the same throughout the solution. (1.7)

homonuclear diatomic molecule A diatomic molecule containing atoms of the same element. (10.7)

homopolymer A polymer that is made from only one type of monomer. (25.2)

Hund’s rule The most stable arrangement of electrons in subshells is the one with the greatest number of parallel spins. (7.8)

hybrid orbitals Atomic orbitals obtained when two or more nonequivalent orbitals of the same atom combine. (10.4)

hybridization The process of mixing the atomic orbitals in an atom (usually the central atom) to generate a set of new atomic orbitals. (10.4)

hydrates Compounds that have a specific number of water molecules attached to them. (2.7)

hydration A process in which an ion or a molecule is surrounded by water molecules arranged in a specific manner. (4.1)

hydrocarbons Compounds made up only of carbon and hydrogen. (24.1)

hydrogen bond A special type of dipole-dipole interaction between the hydrogen atom bonded to an atom of a very electronegative element (F, N, O) and another atom of one of the three electronegative elements. (11.2)

hydrogenation The addition of hydrogen, especially to compounds with double and triple carbon-carbon bonds. (22.2)

hydronium ion The hydrated proton, H3O+. (4.3)

hydrophilic Water-loving. (12.8)

hydrophobic Water-fearing. (12.8)

hypothesis A tentative explanation for a set of observations. (1.2)

I

ideal gas A hypothetical gas whose pressure-volume-temperature behavior can be completely accounted for by the ideal gas equation. (5.4)

ideal gas equation An equation expressing the relationships among pressure, volume, temperature, and amount of gas (PV = nRT, where R is the gas constant). (5.4)

ideal solution Any solution that obeys Raoult’s law. (12.6)

indicators Substances that have distinctly different colors in acidic and basic media. (4.7)

induced dipole The separation of positive and negative charges in a neutral atom (or a nonpolar molecule) caused by the proximity of an ion or a polar ­molecule. (11.2)

inert complex A complex ion that undergoes very slow ligand exchange reactions. (23.5)

inert pair effect The tendency for heavier Group 13 to 16 atoms to form ions with charges two less than their normal valency. (8.2)

inorganic compounds Compounds other than organic compounds. (2.7)

insulator A substance incapable of conducting electricity. (21.3)

intensive property A property that does not depend on how much matter is being considered. (1.9)

intermediate A species that appears in the mechanism of the reaction (that is, the ­elementary steps) but not in the overall balanced equation. (13.5)

intermolecular forces Attractive forces that exist among molecules. (11.2)

International System of Units (SI) A system of units based on metric units. (1.3)

intramolecular forces Forces that hold atoms together in a molecule. (11.2)

ion An atom or a group of atoms that has a net positive or negative charge. (2.5)

ion pair One or more cations and one or more anions held together by electrostatic forces. (12.7)

ion-dipole forces Forces that operate between an ion and a dipole. (11.2)

ion-product constant Product of hydrogen ion concentration and hydroxide ion concentration (both in molarity) at a particular temperature. (15.2)

ionic bond The electrostatic force that holds ions together in an ionic compound. (9.2)

ionic compound Any neutral compound containing cations and anions. (2.5)

ionic equation An equation that shows dissolved species as free ions. (4.2)

ionic radius The radius of a cation or an anion as measured in an ionic ­compound. (8.3)

ionization energy (IE) The minimum energy required to remove an electron from an isolated atom (or an ion) in its ground state. (8.4)

ionosphere The uppermost layer of the atmosphere. (20.1)

isoelectronic Ions, or atoms and ions, that possess the same number of electrons, and hence the same ground-state electron configuration, are said to be ­isoelectronic. (8.2)

isolated system A system that does not allow the transfer of either mass or energy to or from its surroundings. (6.2)

isotopes Atoms having the same atomic number but different mass numbers. (2.3)

J

Joule (J) Unit of energy given by newtons × meters. (5.7)

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K

kelvin The SI base unit of temperature. (1.3)

Kelvin temperature scale A temperature scale that uses the absolute zero of temperature as the lowest temperature. (5.3).

ketones Compounds with a carbonyl functional group and the general formula RR′CO, where R and R′ are alkyl and/or aromatic groups. (24.4)

kinetic energy (Ek) Energy available because of the motion of an object. (5.7)

kinetic molecular theory of gases Treatment of gas behavior in terms of the random motion of molecules. (5.7)

L

labile complex Complexes that undergo rapid ligand exchange reactions. (23.5)

lanthanoids (rare earth) series Elements that have incompletely filled 4f subshells or readily give rise to cations that have incompletely filled 4f subshells. (7.9)

lattice A three-dimensional array of cations and anions. (2.6)

lattice energy (U) The energy required to completely separate one mole of a solid ionic compound into gaseous ions. (6.7)

law A concise verbal or mathematical statement of a relationship between phenomena that is always the same under the same conditions. (1.2)

law of conservation of energy The total quantity of energy in the universe is constant. (6.1)

law of conservation of mass Hypothesis stating that matter can be neither created nor destroyed. (2.1)

law of definite proportions Different samples of the same compound always contain its constituent elements in the same proportions by mass. (2.1)

law of mass action For a reversible reaction at equilibrium and a constant temperature, a certain ratio of reactant and product concentrations has a constant value, K (the equilibrium constant). (14.1)

law of multiple proportions If two elements can combine to form more than one type of compound, the masses of one element that combine with a fixed mass of the other element are in ratios of small whole numbers. (2.1)

Le Châtelier’s principle If an external stress is applied to a system at equilibrium, the system will adjust itself in such a way as to partially offset the stress as the system reaches a new equilibrium position. (14.5)

Lewis acid A substance that can accept a pair of electrons. (15.12)

Lewis base A substance that can donate a pair of electrons. (15.12)

Lewis dot symbol The symbol of an element with one or more dots that represent the number of valence electrons in an atom of the element. (9.1)

Lewis structure A representation of covalent bonding using Lewis symbols. Shared electron pairs are shown either as lines or as pairs of dots between two atoms, and lone pairs are shown as pairs of dots on individual atoms. (9.4)

ligand A molecule or an ion that is bonded to the metal ion in a complex ion. (23.2)

limiting reagent The reactant used up first in a reaction. (3.9)

line spectra Spectra produced when radiation is absorbed or emitted by substances only at some wavelengths. (7.3)

liter The volume occupied by one cubic decimeter. (1.3)

lone pairs Valence electrons that are not involved in covalent bond formation. (9.4)

M

macroscopic properties Properties that can be measured directly. (1.3)

manometer A device used to measure the pressure of gases. (5.2)

many-electron atoms Atoms that contain two or more electrons. (7.5)

mass A measure of the quantity of matter contained in an object. (1.9)

mass defect The difference between the mass of an atom and the sum of the masses of its protons, neutrons, and electrons. (19.2)

mass number (A) The total number of neutrons and protons present in the nucleus of an atom. (2.3)

matter Anything that occupies space and possesses mass. (1.7)

melting point The temperature at which solid and liquid phases coexist in equilibrium. (11.8)

mesosphere A region between the stratosphere and the ionosphere. (20.1)

metalloid An element with properties ­intermediate between those of metals and nonmetals. (2.4)

metallurgy The science and technology of separating metals from their ores and of compounding alloys. (21.2)

metals Elements that are good conductors of heat and electricity and have the ­tendency to form positive ions in ionic compounds. (2.4)

metathesis reaction A reaction that involves the exchange of parts between two compounds. (4.2)

microscopic properties Properties that cannot be measured directly without the aid of a microscope or other special instrument. (1.3)

mineral A naturally occurring substance with a range of chemical composition. (21.1)

miscible Two liquids that are completely soluble in each other in all proportions are said to be miscible. (12.2)

mixture A combination of two or more substances in which the substances retain their identity. (1.7)

moderator A substance that can reduce the kinetic energy of neutrons. (19.5)

molality The number of moles of solute dissolved in 1 kg of solvent. (12.3)

molar concentration See molarity.

molar heat of fusion (ΔHfus) The energy (in kilojoules) required to melt 1 mole of a solid. (11.8)

molar heat of sublimation (ΔHsub) The energy (in kilojoules) required to sublime 1 mole of a solid. (11.8)

molar heat of vaporization (ΔHvap) The energy (in kilojoules) required to vaporize 1 mole of a liquid. (11.8)

molar mass (ℳ) The mass (in grams or kilograms) of one mole of atoms, molecules, or other particles. (3.2)

molar solubility The number of moles of solute in 1 liter of a saturated solution (mol/L). (16.5)

molarity (M) The number of moles of solute in 1 liter of solution. (4.5)

mole (mol) The amount of substance that contains as many elementary entities (atoms, molecules, or other particles) as there are atoms in exactly 12 g (or 0.012 kg) of the carbon-12 isotope. (3.2)

mole fraction Ratio of the number of moles of one component of a mixture to the total number of moles of all components in the mixture. (5.6)

mole method An approach for determining the amount of product formed in a reaction. (3.8)

molecular equations Equations in which the formulas of the compounds are written as though all species existed as molecules or whole units. (4.2)

molecular formula An expression showing the exact numbers of atoms of each element in a molecule. (2.6)

molecular mass The sum of the atomic masses (in atomic mass units) present in the molecule. (3.3)

molecular orbital An orbital that results from the interaction of the atomic orbitals of the bonding atoms. (10.6)

molecularity of a reaction The number of molecules reacting in an elementary step. (13.5)

molecule An aggregate of at least two atoms in a definite arrangement held together by special forces. (2.5)

monatomic ion An ion that contains only one atom. (2.5)

monomer The single repeating unit of a polymer. (25.2)

monoprotic acid Each unit of the acid yields one hydrogen ion upon ionization. (4.3)

multiple bonds Bonds formed when two atoms share two or more pairs of electrons. (9.4)

N

n-type semiconductors Semiconductors that contain donor impurities. (21.3)

Nernst equation The relation between the emf of a galvanic cell and the standard emf and the concentrations of the oxidizing and reducing agents. (18.5)

net ionic equation An equation that indicates only the ionic species that actually take part in the reaction. (4.2)

Page G-6

neutralization reaction A reaction between an acid and a base. (4.3)

neutron A subatomic particle that bears no net electric charge. Its mass is slightly greater than a proton’s mass. (2.2)

newton (N) The SI unit for force. (5.2)

nitrogen fixation The conversion of molecular nitrogen into nitrogen compounds. (20.1)

noble gas core The electron configuration of the noble gas element that most nearly precedes the element being considered. (7.9)

noble gases Nonmetallic elements in Group 8A (He, Ne, Ar, Kr, Xe, and Rn). (2.4)

node The point at which the amplitude of the wave is zero. (7.1, 7.4)

nonelectrolyte A substance that, when dissolved in water, gives a solution that is not electrically conducting. (4.1)

nonmetals Elements that are usually poor conductors of heat and electricity. (2.4)

nonpolar molecule A molecule that does not possess a dipole moment. (10.2)

nonvolatile Does not have a measurable vapor pressure. (12.6)

nuclear binding energy The energy required to break up a nucleus into its protons and neutrons. (19.2)

nuclear chain reaction A self-sustaining sequence of nuclear fission reactions. (19.5)

nuclear fission A heavy nucleus (mass number > 200) divides to form smaller nuclei of intermediate mass and one or more neutrons. (19.5)

nuclear fusion The combining of small nuclei into larger ones. (19.6)

nuclear transmutation The change undergone by a nucleus as a result of bombardment by neutrons or other particles. (19.1)

nucleic acids High molar mass polymers that play an essential role in protein ­synthesis. (25.4)

nucleon A general term for the protons and neutrons in a nucleus. (19.2)

nucleotide The repeating unit in each strand of a DNA molecule, which consists of a base-deoxyribose-phosphate linkage. (25.4)

nucleus The central core of an atom. (2.2)

O

octet rule An atom other than hydrogen tends to form bonds until it is surrounded by eight valence electrons. (9.4)

open system A system that can exchange mass and energy (usually in the form of heat) with its surroundings. (6.2)

optical isomers Compounds that are nonsuperimposable mirror images. (23.3)

ore The material of a mineral deposit in a sufficiently concentrated form to ­allow economical recovery of a desired metal. (21.1)

organic chemistry The branch of chemistry that deals with carbon compounds. (24.1)

organic compounds Compounds that contain carbon, usually in combination with elements such as hydrogen, oxygen, nitrogen, and sulfur. (2.7)

osmosis The net movement of solvent ­molecules through a semipermeable ­membrane from a pure solvent or from a dilute solution to a more concentrated ­solution. (12.6)

osmotic pressure (π) The pressure required to stop osmosis. (12.6)

overvoltage The difference between the electrode potential and the actual voltage required to cause electrolysis. (18.8)

oxidation number The number of charges an atom would have in a molecule if electrons were transferred completely in the direction indicated by the difference in electronegativity. (4.4)

oxidation reaction The half-reaction that involves the loss of electrons. (4.4)

oxidation state See oxidation number.

oxidation-reduction (redox) reaction A reaction that involves the transfer of electron(s) or the change in the oxidation state of reactants. (4.4)

oxidizing agent A substance that can accept electrons from another substance or increase the oxidation numbers in another substance. (4.4)

oxoacid An acid containing hydrogen, oxygen, and another element (the central element). (2.7)

oxoanion An anion derived from an oxoacid. (2.7)

P

p-type semiconductors Semiconductors that contain acceptor impurities. (21.3)

paramagnetic Attracted by a magnet. A paramagnetic substance contains one or more unpaired electrons. (7.8)

partial pressure Pressure of one component in a mixture of gases. (5.6)

pascal (Pa) A pressure of one newton per square meter (1 N/m2). (5.2)

Pauli exclusion principle No two electrons in an atom can have the same four quantum numbers. (7.8)

percent by mass The ratio of the mass of a solute to the mass of the solution, multiplied by 100 percent. (12.3)

percent composition by mass The percent by mass of each element in a compound. (3.5)

percent ionization Ratio of ionized acid concentration at equilibrium to the initial concentration of acid. (15.5)

percent yield The ratio of actual yield to theoretical yield, multiplied by 100 percent. (3.10)

period A horizontal row of the periodic table. (2.4)

periodic table A tabular arrangement of the elements. (2.4)

pH The negative logarithm of the hydrogen ion concentration. (15.3)

phase A homogeneous part of a system in contact with other parts of the system but separated from them by a well-defined boundary. (11.1)

phase boundary The boundaries separating different phases in a phase diagram. (11.9)

phase change Transformation from one phase to another. (11.8)

phase diagram A diagram showing the conditions at which a substance exists as a solid, liquid, or vapor. (11.9)

photochemical smog Formation of smog by the reactions of automobile exhaust in the presence of sunlight. (20.7)

photoelectric effect A phenomenon in which electrons are ejected from the surface of certain metals exposed to light of at least a certain minimum frequency. (7.2)

photon A particle of light. (7.2)

physical equilibrium An equilibrium in which only physical properties change. (14.1)

physical property Any property of a substance that can be observed without transforming the substance into some other substance. (1.9)

pi (π) bond A covalent bond formed by ­sideways overlapping orbitals; its electron density is concentrated above and below the plane of the nuclei of the bonding ­atoms. (10.5)

pi molecular orbital A molecular orbital in which the electron density is concentrated above and below the plane of the two nuclei of the bonding atoms. (10.6)

plasma A gaseous mixture of positive ions and electrons. (19.6)

polar covalent bond In such a bond, the electrons spend more time in the vicinity of one atom than the other. (9.5)

polar molecule A molecule that possesses a dipole moment. (10.2)

polarimeter The instrument for measuring the rotation of polarized light by optical isomers. (23.3)

polyatomic ion An ion that contains more than one atom. (2.5)

polyatomic molecule A molecule that consists of more than two atoms. (2.5)

polymer A compound distinguished by a high molar mass, ranging into thousands and millions of grams, and made up of many repeating units. (25.1)

positron A particle that has the same mass as the electron, but bears a + 1 charge. (19.1)

positron emission A type of radioactive decay in which a positron is emitted from a nucleus. (19.2)

potential energy Energy available by virtue of an object’s position. (6.1)

precipitate An insoluble solid that separates from the solution. (4.2)

precipitation reaction A reaction that results in the formation of a precipitate. (4.2)

precision The closeness of agreement of two or more measurements of the same quantity. (1.4)

pressure Force applied per unit area. (5.2)

product The substance formed as a result of a chemical reaction. (3.7)

protein Polymers of amino acids. (25.3)

proton A subatomic particle having a single positive electric charge. The mass of a proton is about 1840 times that of an electron. (2.2)

pyrometallurgy Metallurgical processes that are carried out at high temperatures. (21.2)

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Q

qualitative Consisting of general observations about the system. (1.2)

qualitative analysis The determination of the types of ions present in a solution. (16.8)

quantitative Comprising numbers obtained by various measurements of the system. (1.2)

quantitative analysis The determination of the amount of substances present in a sample. (4.5)

quantum The smallest quantity of energy that can be emitted (or absorbed) in the form of electromagnetic radiation. (7.1)

quantum numbers Numbers that describe the distribution of electrons in hydrogen and other atoms. (7.6)

R

racemic mixture An equimolar mixture of the two enantiomers. (23.3)

radiant energy Energy transmitted in the form of waves. (6.1)

radiation The emission and transmission of energy through space in the form of particles and/or waves. (2.2)

radical Any neutral fragment of a molecule containing an unpaired electron. (19.8)

radioactive decay series A sequence of nuclear reactions that ultimately result in the formation of a stable isotope. (19.3)

radioactivity The spontaneous breakdown of an atom by emission of particles and/or radiation. (2.2)

random errors Errors that are not predictable, leading to measured values that vary greatly from the true value. (1.4)

Raoult’s law The vapor pressure of the solvent over a solution is given by the product of the vapor pressure of the pure solvent and the mole fraction of the solvent in the solution. (12.6)

rare earth series See lanthanide series.

rate constant (k) Constant of proportionality between the reaction rate and the concentrations of reactants. (13.1)

rate law An expression relating the rate of a reaction to the rate constant and the concentrations of the reactants. (13.2)

rate-determining step The slowest step in the sequence of steps leading to the formation of products. (13.5)

reactant The starting substance in a chemical reaction. (3.7)

reaction mechanism The sequence of elementary steps that leads to product formation. (13.5)

reaction order The sum of the powers to which all reactant concentrations appearing in the rate law are raised. (13.2)

reaction quotient (Qc) A number equal to the ratio of product concentrations to reactant concentrations, each raised to the power of its stoichiometric coefficient at some point other than equilibrium. (14.4)

reaction rate The change in the concen­tration of reactant or product with time. (13.1)

redox reaction See oxidation-reduction reaction.

reducing agent A substance that can donate electrons to another substance or decrease the oxidation numbers in another ­substance. (4.4)

reduction reaction The half-reaction that involves the gain of electrons. (4.4)

representative elements Elements in Groups 1A through 7A, all of which have incompletely filled s or p subshells of highest principal quantum number. (8.2)

resonance The use of two or more Lewis structures to represent a particular molecule. (9.8)

resonance structure One of two or more alternative Lewis structures for a molecule that cannot be described fully with a single Lewis structure. (9.8)

reversible reaction A reaction that can occur in both directions. (4.1)

ribonucleic acid (RNA) A form of nucleic acid. (25.4)

root-mean-square (rms) speed (urms) A measure of the average molecular speed at a given temperature. (5.7)

S

salt An ionic compound made up of a cation other than H+ and an anion other than OH− or O2−. (4.3)

salt hydrolysis The reaction of the anion or cation, or both, of a salt with water. (15.10)

saponification Soapmaking. (24.4)

saturated hydrocarbons Hydrocarbons that contain the maximum number of hydrogen atoms that can bond with the number of carbon atoms present. (24.2)

saturated solution At a given temperature, the solution that results when the maximum amount of a substance has dissolved in a solvent. (12.1)

scientific method A systematic approach to research. (1.2)

second law of thermodynamics The entropy of the universe increases in a spontaneous process and remains unchanged in an equilibrium process. (17.3)

second-order reaction A reaction whose rate depends on reactant concentration raised to the second power or on the concentrations of two different reactants, each raised to the first power. (13.3)

semiconductors Elements that normally cannot conduct electricity, but can have their conductivity greatly enhanced either by raising the temperature or by adding certain impurities. (21.3)

semipermeable membrane A membrane that enables solvent molecules to pass through, but blocks the movement of solute molecules. (12.6)

sigma (σ) bond A covalent bond formed by orbitals overlapping end-to-end; its electron density is concentrated between the nuclei of the bonding atoms. (10.5)

sigma molecular orbital A molecular orbital in which the electron density is concentrated around a line between the two nuclei of the bonding atoms. (10.6)

significant figures The number of meaningful digits in a measured or calculated quantity. (1.4)

single bond Two atoms are held together by one electron pair. (9.4)

solubility The maximum amount of solute that can be dissolved in a given quantity of solvent (commonly 1 L) at a specific temperature. (4.2, 16.5)

solubility product (Ksp) The product of the molar concentrations of the constituent ions, each raised to the power of its stoichiometric coefficient in the equilibrium equation. (16.5)

solute The substance present in smaller amount in a solution. (4.1)

solution A homogeneous mixture of two or more substances. (4.1)

solvation The process in which an ion or a molecule is surrounded by solvent ­molecules arranged in a specific manner. (12.2)

solvent The substance present in the larger amount in a solution. (4.1)

specific heat (c) The amount of heat energy required to raise the temperature of one gram of a substance by one degree Celsius. (6.5)

spectator ions Ions that are not involved in the overall reaction. (4.2)

spectrochemical series A list of ligands arranged in increasing order of their abilities to split the d orbital energy levels. (23.4)

standard atmospheric pressure (1 atm) The pressure that supports a column of mercury exactly 76 cm high at 0°C at sea level. (5.2)

standard emf (E°cell) The difference of the standard reduction potential of the substance that undergoes reduction and the standard reduction potential of the substance that undergoes oxidation. (18.3)

standard entropy of reaction The entropy change when the reaction is carried out under standard-state conditions. (17.3)

standard enthalpy of formation The heat change that results when one mole of a compound is formed from its elements in their standard states. (6.6)

standard enthalpy of reaction The enthalpy change when the reaction is carried out under standard-state conditions. (6.6)

standard Gibbs-energy of formation The Gibbs-energy change when 1 mole of a compound is synthesized from its elements in their standard states. (17.4)

standard Gibbs-energy of reaction The Gibbs-energy change when the reaction is carried out under standard-state conditions. (17.4)

standard reduction potential The voltage measured as a reduction reaction occurs at the electrode when all solutes are 1 M and all gases are at 1 atm. (18.3)

standard solution A solution of accurately known concentration. (4.7)

standard state The condition of 1 atm of pressure. (6.6)

standard temperature and pressure (STP)

0°C and 1 atm. (5.4)

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state function A property that is determined by the state of the system. (6.3)

state of a system The values of all pertinent macroscopic variables (for example, composition, volume, pressure, and temperature) of a system. (6.3)

stereoisomers Compounds that are made up of the same types and numbers of atoms bonded together in the same sequence but with different spatial arrangements. (23.3)

stoichiometric amounts The exact molar amounts of reactants and products that appear in the balanced chemical equation. (3.9)

stoichiometry The quantitative study of ­reactants and products in a chemical reaction. (3.8)

stratosphere The region of the atmosphere extending upward from the troposphere to about 50 km from Earth. (20.1)

strong acids Strong electrolytes that are assumed to ionize completely in water. (15.4)

strong bases Strong electrolytes that are assumed to ionize completely in water. (15.4)

strong nuclear force The force that holds particles together in the atomic nucleus. (19.2)

structural formula A chemical formula that shows how atoms are bonded to one another in a molecule. (2.6)

structural isomers Molecules that have the same molecular formula but different structures. (24.2)

sublimation The process in which molecules go directly from the solid into the vapor phase. (11.8)

substance A form of matter that has a definite or constant composition (the number and type of basic units present) and distinct properties. (1.7)

substitution reaction A reaction in which an atom or group of atoms replaces an atom or groups of atoms in another molecule. (24.3)

supercooling Cooling of a liquid below its freezing point without forming the solid. (11.8)

supersaturated solution A solution that contains more of the solute than is present in a saturated solution. (12.1)

surface tension The amount of energy required to stretch or increase the surface of a liquid by a unit area. (11.3)

surroundings The rest of the universe outside a system. (6.2)

system Any specific part of the universe that is of interest to us. (6.2)

systematic errors Errors that occur in a ­predictable manner, leading to measured values that are constantly off from the true value. (1.4)

T

termolecular reaction An elementary step that involves three molecules. (13.5)

ternary compounds Compounds consisting of three elements. (2.7)

theoretical yield The amount of product ­predicted by the balanced equation when all of the limiting reagent has ­reacted. (3.10)

theory A unifying principle that explains a body of facts and the laws that are based on them. (1.2)

thermal energy Energy associated with the random motion of atoms and ­molecules. (6.1)

thermochemical equation An equation that shows both the mass and enthalpy relations. (6.4)

thermochemistry The study of heat changes in chemical reactions. (6.2)

thermodynamics The scientific study of the interconversion of heat and other forms of energy. (6.3)

thermonuclear reactions Nuclear fusion reactions that occur at very high temperatures. (19.6)

thermosphere The region of the atmosphere in which the temperature increases continuously with altitude. (20.1)

third law of thermodynamics The entropy of a perfect crystalline substance is zero at the absolute zero of temperature. (17.3)

titration The gradual addition of a solution of accurately known concentration to another solution of unknown concentration until the chemical reaction between the two solutions is complete. (4.7)

tracers Isotopes, especially radioactive isotopes, that are used to trace the path of the atoms of an element in a chemical or ­biological process. (19.7)

transition metals Elements that have incompletely filled d subshells or readily give rise to cations that have incompletely filled d subshells. (7.9)

transition state See activated complex.

transuranium elements Elements with atomic numbers greater than 92. (19.4)

triple bond Two atoms are held together by three pairs of electrons. (9.4)

triple point The point at which the vapor, liquid, and solid states of a substance are in equilibrium. (11.9)

triprotic acid Each unit of the acid yields three protons (H+) upon ionization. (4.3)

troposphere The layer of the atmosphere which contains about 80 percent of the total mass of air and practically all of the atmosphere’s water vapor. (20.1)

U

unimolecular reaction An elementary step in which only one reacting molecule participates. (13.5)

unit cell The basic repeating unit of the arrangement of atoms, molecules, or ions in a crystalline solid. (11.4)

unsaturated hydrocarbons Hydrocarbons that contain carbon-carbon double bonds or carbon-carbon triple bonds. (24.2)

unsaturated solution A solution that contains less solute than it has the capacity to dissolve. (12.1)

V

valence electrons The outer electrons of an atom, which are those involved in chemical bonding. (8.2)

valence shell The outermost electron-occupied shell of an atom, which holds the electrons that are usually involved in bonding. (10.1)

valence-shell electron-pair repulsion (VSEPR) model A model that accounts for the geometrical arrangements of shared and unshared electron pairs around a central atom in terms of the repulsions between electron pairs. (10.1)

van der Waals equation An equation that describes the P, V, and T of a nonideal gas. (5.8)

van der Waals forces The dipole-dipole, dipole-induced dipole, and dispersion forces. (11.2)

van’t Hoff factor (i) The ratio of actual number of particles in solution after dissociation to the number of formula units initially dissolved in solution. (12.7)

vaporization The escape of molecules from the surface of a liquid; also called evaporation. (11.8)

viscosity A measure of a fluid’s resistance to flow. (11.3)

volatile Has a measurable vapor pressure. (12.6)

volume It is the length cubed. (1.9)

W

wave A vibrating disturbance by which energy is transmitted. (7.1)

wavelength (λ) The distance between identical points on successive waves. (7.1)

weak acids Weak electrolytes that ionize only to a limited extent in water. (15.4)

weak bases Weak electrolytes that ionize only to a limited extent in water. (15.4)

weight The force that gravity exerts on an object. (1.3)

work Directed energy change resulting from a process. (6.1)

work function (Φ) The amount of energy binding an electron in a metal. (7.1)

X

X-ray diffraction The scattering of X rays by the units of a regular crystalline solid. (11.5)