Appendix M | Glossary

Absolute rate theory (see transition state theory) (7.6)

Absolute zero (2.3)

Minimum possible temperature, labeled 0 K (zero kelvins); temperature at which the volume of a gas would be zero according to Charles’s law

Accuracy (III)

How closely a measurement aligns with a correct value

Acid ionization (5.1)

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 (K_a) (5.3)

Equilibrium constant for an acid ionization reaction

Acid-base indicator (6.3)

Weak acid or base whose conjugate partner imparts a different solution color; color change indicates the equivalence point of a titration; used in visual assessments of solution pH

Acidic (5.2)

A solution in which [H₃O⁺] > [OH⁻]

Actinide (V)

Inner transition metal in the bottom of the bottom two rows of the periodic table

Activated complex (7.5)

Unstable combination of reactant species formed during a chemical reaction; corresponds to the highest energy transitional point in the elementary step

Activation energy (E_a) (7.5)

Minimum amount of kinetic energy molecules must possess in order for an effective collision to occur and for a reaction to take place

Actual yield (1.3)

The actual amount of product formed in a chemical reaction

Alkali metal (V)

Element in group 1; e.g. Li, Na, K

Alkaline earth metal (V)

Element in group 2; e.g. Mg, Ca, Sr

Alpha particle (α particle) (IV)

Type of radioactive emission producing a positively charged particle consisting of two protons and two neutrons (equivalent to a helium nucleus)

Amontons’s law (see Gay-Lussac’s law) (2.4)

Amphipathic (1.4)

Describes molecules possessing both hydrophobic (nonpolar; water-fearing) and hydrophilic (polar; water-loving) parts

Amphiphilic (see amphipathic) (1.4)

Amphiprotic (5.2)

Species that can act as a proton donor or a proton acceptor in a Bronsted-Lowry acid-base reaction

Amphoteric (5.2)

Species that can act as either an acid or a base

Amplitude (8.1)

Magnitude of the wave’s displacement, corresponding to one-half the height between peaks and troughs; related to the intensity of a wave

Analyte (6.3)

Chemical species of interest of unknown concentration

Angular momentum quantum number (ℓ) (8.4)

Quantum number distinguishing the different shapes of orbitals; it is also a measure of the orbital angular momentum

Anion (V)

Species with an overall negative charge; e.g. chloride ion (Cl^–), phosphate ion (PO₄^3-), acetate ion (CH₃COO^–)

Aqueous solution (1.4)

Solution for which water is the solvent

Arrhenius acid (5.1)

Compound that increases the hydrogen ion concentration in aqueous solution

Arrhenius base (5.1)

Compound that increases the hydroxide ion concentration in aqueous solution

Arrhenius equation (7.5)

Mathematical relationship between a reaction’s rate constant, activation energy, and temperature

Atmospheric pressure (2.3)

Pressure that the air exerts on the surface of the Earth

Atom (I)

Smallest particle of an element that maintains the identity of that element and can enter into a chemical combination

Atomic mass (V)

Average mass of atoms of an element (calculated as the weighted average of the masses of the isotopes that compose an element), expressed in amu

Atomic mass unit (amu) (V)

Unit of mass equal to

of the mass of a ¹²C atom

Atomic number (Z) (V)

Number of protons in the nucleus of an atom

Atomic orbital (8.4)

Mathematical function that describes the behavior of an electron in an atom (also called the wavefunction); defines a specific set of principal, angular momentum, and magnetic quantum numbers for an electron

Aufbau principle (8.5)

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; electrons fill the lowest energy orbitals first

Autoionization (5.2)

Reaction between identical species yielding ionic products; for water, this reaction involves water molecules acting as both acids (proton donors) and bases (proton acceptors) with each other to yield hydronium and hydroxide ions

Average rate of reaction (7.2)

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 law (2.4)

Volume of a gas at constant temperature and pressure is proportional to the number of gas molecules

Avogadro’s number (N_A) (1.1)

The experimentally determined value of the number of entities comprising 1 mole of substance, equal to 6.022 × 10²³ mol⁻¹

Axial position (9.5)

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 (1.2)

Chemical equation with equal numbers of atoms for each element in the reactant and product

Bar (bar) (2.3)

Unit of pressure; 1 bar = 100,000 Pa

Barometer (2.3)

Device used to measure atmospheric pressure

Base ionization (5.1)

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 (K_b) (5.3)

Equilibrium constant for a base ionization reaction

Basic (5.2)

A solution in which [H₃O⁺] < [OH⁻]

Bimolecular reaction (7.7)

Elementary reaction involving two reactant species

Binary acid (VII)

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); e.g. HCl, HBr, H₂S

Binary compound (VI)

Compound containing two different elements

Blackbody (8.1)

Idealized perfect absorber of all incident electromagnetic radiation; such bodies emit electromagnetic radiation in characteristic continuous spectra called blackbody radiation

Bohr’s model (8.2)

Structural model in which an electron moves around the nucleus only in circular orbits, each with a specific allowed radius

Bomb calorimeter (3.5)

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 (9.5)

Angle between any two covalent bonds that share a common atom

Bond dipole moment (9.5)

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 dissociation energy (BE) (9.3)

Energy required to break a covalent bond in a gaseous substance

Bond distance (see bond length) (9.5)

Bond energy (see bond dissociation energy (BE)) (9.3)

Bond length (9.5)

Distance between the nuclei of two bonded atoms at which the lowest potential energy is achieved

Bond order (9.4)

Number of pairs of electrons between two atoms; it can be found by the number of bonds in a Lewis structure or by the difference between the number of bonding and antibonding electrons divided by two

Boyle’s law (2.4)

Volume of a given number of moles of gas held at constant temperature is inversely proportional to the pressure under which it is measured

Brønsted-Lowry acid (5.1)

Any species that can donate a proton to another molecule

Brønsted-Lowry base (5.1)

Any species that can accept a proton from another molecule

Buffer (6.2)

Mixture of appreciable amounts of a weak acid-base pair; the buffer resists dramatic changes in pH when small amounts of acid or base are added

Buffer capacity (6.2)

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); in other words, the amount of acid or base a buffer can counteract

Buret (6.3)

Precisely calibrated volumetric delivery tube used for the precise delivery of variable liquid volumes, such as in a titration analysis

Calorie (cal) (3.1)

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 (3.5)

Device used to measure the amount of heat absorbed or released in a chemical or physical process

Calorimetry (3.5)

Process of measuring enthalpy changes for chemical reactions

Catalyst (7.1)

Substance that lowers the activation energy of a specific reaction by providing an alternate reaction pathway, thereby increasing the rate of a reaction without itself being consumed by the reaction

Cation (V)

Species with an overall positive charge; e.g. Ca²⁺, NH₄⁺, H₃O⁺

Celsius (°C) (II)

Unit of temperature; water freezes at 0°C and boils at 100°C on this scale

Charles’s law (2.4)

Volume of a given number of moles of gas is directly proportional to its kelvin temperature when the pressure is held constant

Chemical change (I)

Change producing a different kind of matter from the original kind of matter; it is the process of demonstrating a chemical property

Chemical equation (1.2)

Concise way, using symbols or formulas, of representing a chemical reaction

Chemical property (I)

Behavior that is related to the change of one kind of matter into another kind of matter; it is a characteristic that describes how matter changes form in the presence of other matter

Chemical symbol (V)

One-, two-, or three-letter abbreviation used to represent an element or its atoms; e.g. C (for carbon), Cu (for copper), Xe (for xenon)

Chemical thermodynamics (3.2)

Area of science that deals with the relationships between heat, work, and all forms of energy associated with chemical and physical processes

Chemistry (I)

Study of the composition, properties, and interactions of matter with other matter and with energy

Closed system (3.1)

System that can exchange energy but not matter with its surroundings

Coefficient (1.2)

The number placed in front of symbols or formulas in a chemical equation indicating their relative amount and placed when there’s more than one molecule of a substance

Collision theory (7.5)

Model that emphasizes the energy and orientation of molecular collisions in chemical reactions to explain and predict reaction kinetics

Colour-change interval (6.3)

Range in pH over which the color change of an indicator is observed

Combustion analysis (1.2)

Gravimetric technique used to determine the elemental composition of a compound via the collection and weighing of its gaseous combustion products

Combustion reaction (1.5)

Redox chemical reaction in which a reactant combines with oxygen to produce oxides of all other elements as products; produces significant amounts of energy in the form of heat and, sometimes, light

Common ion effect (6.1)

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 (1.4)

The chemical equation in which all dissolved ionic reactants and products, including spectator ions, are explicitly represented by formulas for their dissociated ions

Compound (I)

Pure substance that can be decomposed into two or more elements

Compressibility factor (Z) (2.8)

Ratio of the experimentally measured molar volume for a gas to its molar volume as computed from the ideal gas equation; measure of the extent of deviation from ideal gas behaviour

Concentrated (1.4)

The qualitative term for a solution containing solute at a relatively high concentration

Concentration (C) (1.4)

A quantitative measure of the amount of solute dissolved in a given amount of solvent

Conjugate acid (5.1)

Substance formed when a base gains a proton

Conjugate base (5.1)

Substance formed when an acid loses a proton

Continuous spectrum (8.1)

Electromagnetic radiation given off in an unbroken series of wavelengths, containing all colours of light (e.g., white light from the sun)

Coordinate covalent bond (5.6)

Covalent bond in which both electrons originated from the same atom

Core electron (8.5)

Electron in an atom that occupies the orbitals of the inner shells

Covalent bond (VI)

Chemical bond formed by two atoms sharing electrons (attractive force between the nuclei of a molecule’s atoms and pairs of electrons between the atoms)

Covalent radius (8.7)

One-half the distance between the nuclei of two identical atoms when they are joined by a covalent bond

Cubic centimetre (cm³ or cc) (II)

Volume of a cube with an edge length of exactly 1 cm

Cubic metre (m³) (II)

SI unit of volume; volume of a cube with an edge length of exactly 1 m

d orbital (8.4)

Region of space with high electron density that is either four lobed or contains a dumbbell and torus shape; describes orbitals with ℓ = 2.

Dalton (Da) (V)

Alternative unit equivalent to the atomic mass unit

Dalton’s atomic theory (IV)

Set of postulates that established the fundamental properties of atoms

Dalton’s law of partial pressures (2.5)

Total pressure of a mixture of ideal gases is equal to the sum of the partial pressures of the component gases

Dative bond (see coordinate covalent bond) (5.6)

Degenerate orbitals (8.4)

Orbitals that have the same energy

Density (ρ) (II)

A physical property defined as the ratio of mass to volume for a substance or object

Diamagnetism (8.6)

Magnetic state of substances characterized by paired electrons; diamagnetic substances are (weakly) repelled by an applied magnetic field

Differential rate law (see rate law) (7.3)

Diffusion (2.7)

Movement of an atom or molecule from a region of relatively high concentration to one of relatively low concentration (discussed in Chapter 2 with regard to gaseous species, but applicable to species in any phase)

Dilute (1.4)

A qualitative term for a solution containing solute at a relatively low concentration; also refers to the act of adding solvent, which decreases the concentration of the solute in the solution

Dilution (1.4)

Process of adding solvent to a solution in order to lower the concentration of solutes

Dimensional analysis (II)

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 (see polar molecule) (9.5)

Dipole moment (9.5)

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 (2.1)

Intermolecular force caused by molecules with a permanent dipole

Diprotic acid (5.4)

Acid containing two ionizable hydrogen atoms per molecule

Diprotic base (5.4)

Base capable of accepting two protons

Dispersion force (2.1)

Intermolecular force between two rapidly fluctuating, temporary dipoles, caused by the instantaneous positions of electrons in molecules; significant only when particles are very close together

Dissociation constant (K_d) (5.6)

Equilibrium constant for the decomposition of a complex ion into its components

Dissolved (1.4)

Describes the process by which solute components are dispersed in a solvent

Double bond (9.4)

Covalent bond in which two pairs of electrons are shared between two atoms

Effective nuclear charge (Z_eff) (8.7)

Charge that leads to the Coulomb force exerted by the nucleus on an electron, calculated as the nuclear charge minus shielding; net nuclear charge felt by valence electrons

Effusion (2.7)

Transfer of gaseous atoms or molecules from a container to a vacuum through very small openings

Electromagnetic radiation (8.1)

Energy transmitted by waves that have an electric-field component and a magnetic-field component

Electromagnetic spectrum (8.1)

Full span of the possible wavelengths, frequencies, and energies that electromagnetic radiation can comprise, including radio, microwaves, infrared, visible, ultraviolet, X-rays, and gamma rays

Electron (e^–) (IV)

Negatively charged, subatomic particle of relatively low mass located outside the nucleus

Electron affinity (EA) (8.7)

Energy change associated with addition of an electron to a gaseous atom or ion

Electron configuration (8.5)

Listing that identifies the electron occupancy of an atom’s shells and subshells

Electron-pair geometry (9.5)

Arrangement around a central atom of all regions of electron density (bonds, lone pairs, or unpaired electrons)

Electronegativity (EN) (9.3)

Relative tendency of an atom to attract electrons in a bond to itself

Element (I)

Substance that is composed of a single type of atom; a substance that cannot be broken down into simpler chemical substances by ordinary chemical means; e.g. hydrogen, zinc, argon

Elementary reaction (7.7)

Reaction that takes place in a single step, precisely as depicted in its chemical equation

Empirical formula (1.2)

Formula showing the composition of a compound given as the simplest whole-number ratio of atoms

Empirical formula mass (1.2)

Sum of average atomic masses for all atoms represented in an empirical formula

Endothermic process (3.2)

Chemical reaction or physical change that absorbs heat

Endpoint (6.3)

Measured volume of titrant solution that yields the change in sample solution appearance (e.g. colour change) or other property expected for stoichiometric equivalence

Energy (E) (3.1)

Capacity to supply heat or do work

Enthalpy (H) (3.4)

Sum of a system’s internal energy and the mathematical product of its pressure and volume

Enthalpy change (ΔH) (3.4)

Heat released or absorbed by a system under constant pressure during a chemical or physical process

Entropy (S) (4.4)

Level of randomness (or disorder) of a system, or a measure of the energy dispersal of the molecules in the system

Equatorial position (9.5)

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 (4.1)

State of a reversible reaction in which the forward and reverse processes occur at equal rates

Equilibrium constant (K) (4.2)

Value of the reaction quotient for a system at equilibrium; relates to the ratio of products and reactants at equilibrium; may be expressed using concentrations (K_c) or partial pressures (K_p)

Equivalence point (6.3)

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

Exact number (III)

Number derived by counting or by definition; technically has an infinite number of significant figures

Excess reactant (1.3)

Reactant present in an amount greater than required by the reaction stoichiometry

Excited electronic state (8.2)

State having an energy greater than the ground-state energy

Excited state (see excited electronic state) (8.2)

Exothermic process (3.2)

Chemical reaction or physical change that releases heat

Expanded octet (9.4)

Describes a hypervalent molecule, which contains at least one main group element that has more than eight electrons in its valence shell

Expansion work (3.3)

Work done as a system expands or contracts against external pressure

Extensive property (I)

Property of a substance that depends on the amount of the substance

f orbital (8.4)

Multilobed region of space with high electron density, describes orbitals with ℓ = 3

Fahrenheit (°F) (2.3)

Unit of temperature; water freezes at 32 °F and boils at 212 °F on this scale

First law of thermodynamics (3.3)

Internal energy of a system changes due to heat flow in or out of the system or work done on or by the system

Formal charge (9.4)

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)

Formation constant (K_f) (5.6)

Equilibrium constant for the formation of a complex ion from its components

Free radical (9.4)

Molecule that contains an odd number of electrons

Frequency (ν) (8.1)

Number of wave cycles (peaks or troughs) that pass a specified point in space per unit time

Fundamental unit of charge (V)

Also called the elementary charge; equals the magnitude of the charge of an electron (e^–) with e = 1.602 × 10⁻¹⁹ C

Gas (I)

State in which matter has neither definite volume nor shape

Gay-Lussac’s law (2.4)

Pressure of a given number of moles of gas is directly proportional to its kelvin temperature when the volume is held constant

Graham’s law of effusion (2.7)

Rates of diffusion and effusion of gases are inversely proportional to the square roots of their molecular masses

Ground electronic state (8.2)

State in which the electrons in an atom, ion, or molecule have the lowest energy possible

Ground state (see ground electronic state) (8.2)

Group (V)

Vertical column of the periodic table

Half-life of a reaction (t_1/2) (7.3)

Amount of time required for the concentration of a reactant to drop to one half of its initial concentration

Half-reaction (1.5)

The individual oxidation or reduction reaction of a redox reaction

Half-reaction method (1.5)

Method of balancing redox reactions by writing and balancing the individual half-reactions

Halogen (V)

Element in group 17; e.g. fluorine (F), chlorine (Cl), bromine (Br)

Heat (q) (3.2)

Transfer of thermal energy between two bodies

Heat capacity (C) (3.5)

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 (8.3)

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

Henderson-Hasselbalch equation (6.2)

Logarithmic version of the acid ionization constant expression, conveniently formatted for calculating the pH of buffer solutions

Hertz (Hz) (8.1)

Unit of frequency, which is the number of cycles per second, s⁻¹

Hess’s law (3.6)

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 (7.8)

Catalyst present in a different phase from one or more of the reactants (e.g. furnishing a surface at which a reaction can occur)

Heterogeneous equilibrium (4.2)

Equilibrium in which reactants and products occupy two or more different phases

Heterogeneous mixture (I)

Combination of substances with a composition that varies from point to point

Homogeneous catalyst (7.8)

Catalyst present in the same phase as the reactants

Homogeneous equilibrium (4.2)

Equilibrium in which all reactants and products occupy the same phase

Homogeneous mixture (I)

Combination of substances with a composition that is uniform throughout

Hund’s rule (8.5)

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

Hydrate (VII)

Compound containing one or more water molecules bound within its crystals; e.g. CuSO₄·5H₂O, CaSO₄·2H₂O

Hydrocarbon (3.6)

Compound composed only of hydrogen and carbon; the major component of fossil fuels

Hydrogen bonding (2.1)

Intermolecular force that occurs when exceptionally strong dipoles attract; these interactions exist when hydrogen is bonded to one of the three most electronegative elements: F, O, or N

Hydronium ion (H₃O⁺) (5.1)

Actual chemical species that represents a hydrogen ion combining with a water molecule in aqueous solution

Hydrophilic (1.4)

The tendency to weakly interact with and not mix well with water molecules

Hydrophobic (1.4)

The tendency to strongly interact with and mix well with water molecules

Hypervalent molecule (see expanded octet) (9.4)

Ideal gas (2.4)

Hypothetical gas whose physical properties are perfectly described by the gas laws; it conforms exactly to the tenets of the kinetic molecular theory

Ideal gas constant (R) (2.4)

Constant derived from the ideal gas equation R = 0.08206 L atm mol^–1 K^–1 or 8.314 L kPa mol^–1 K^–1

Ideal gas law (2.4)

Relation between the pressure, volume, amount, and temperature of a gas under conditions derived by combination of the simple gas laws

Induced dipole (2.1)

Temporary dipole formed when the electrons of an atom or molecule are distorted by the instantaneous dipole of a neighboring atom or molecule

Inert gas (see noble gas) (V)

Initial rate of reaction (7.2)

Instantaneous rate of a chemical reaction at t = 0 s (immediately after the reaction has begun)

Instantaneous dipole (2.1)

Temporary dipole that occurs for a brief moment in time when the electrons of an atom or molecule are distributed asymmetrically

Instantaneous rate of reaction (7.2)

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 (7.3)

Equation that relates the concentration of a reactant to elapsed time of reaction

Intensive property (I)

Property of a substance that is independent of the amount of the substance

Interference pattern (8.1)

Pattern typically consisting of alternating bright and dark fringes; it results from constructive and destructive interference of waves

Intermediate (7.7)

Species produced in one elementary step of a reaction mechanism and consumed in a subsequent step; does not appear in the overall balanced equation

Intermolecular force (2.1)

Non-covalent attractive force between atoms, molecules, and/or ions

Internal energy (U) (3.2)

Total of all possible kinds of energy present in a substance or substances

Ion (V)

Species with an overall electric charge

Ion product (Q) (6.4)

Product of the concentrations of the ions in solution raised to the same powers as in the solubility product expression; analogous to the reaction quotient (Q) discussed for gaseous equilibria

Ion-product constant for water (K_W) (5.2)

Equilibrium constant for the autoionization of water; represents the product of the hydrogen ion and hydroxide ion concentrations; K_W = 1.0 × 10^-14 at 25°C

Ionic bond (VI)

Electrostatic forces of attraction between the oppositely charged ions of an ionic compound

Ionic compound (VI)

Compound composed of cations and anions combined in ratios, yielding an electrically neutral substance; e.g. Na₂SO₄, MgO, NaHCO₃

Ionization energy (IE) (8.7)

Energy required to remove an electron from a gaseous atom or ion

Isoelectronic (8.7)

Group of ions or atoms that have identical electron configurations

Isolated system (3.1)

System that exchanges neither energy nor matter with the surroundings

Isomers (1.2)

Compounds with the same chemical formula but different structures

Isotopes (IV)

Atoms of the same element that contain the same number of protons but different numbers of neutrons; e.g. examples of isotopes for carbon are ¹²C (stable and most abundant), ¹³C (also stable), and ¹⁴C (radioisotope)

Joule (J) (3.1)

SI unit of energy; 1 J = 1 kg m² s^-2 and 4.184 J = 1 cal

Kelvin (K) (II)

SI unit of temperature; 273.15 K = 0 ºC

Kilogram (kg) (II)

Standard SI unit of mass; 1 kg = approximately 2.2 pounds

Kinetic energy (E_k) (3.1)

Energy of a moving body, in joules, equal to 1/2 mv² (where m = mass and v = velocity)

Kinetic molecular theory (2.6)

Theory based on simple principles and assumptions that effectively explains ideal gas behavior by helping us understand gases at the molecular level and their physical properties

Lanthanide (V)

Inner transition metal in the top of the bottom two rows of the periodic table

Lattice energy (ΔH_lattice) (9.2)

Energy required to separate one mole of an ionic solid into its component gaseous ions

Law of conservation of matter (I)

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 (see law of definite proportions) (IV)

Law of definite proportions (IV)

All samples of a pure compound contain the same elements in the same proportions by mass

Law of multiple proportions (IV)

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 Châtelier’s principle (4.4)

An equilibrium subjected to stress will shift in a way to counter the stress and re-establish equilibrium

Length (II)

Measure of one dimension of an object

Leveling effect of water (5.3)

Observation that acid-base strength of solutes in a given solvent is limited to that of the solvent’s characteristic acid and base species (in water, hydronium and hydroxide ions, respectively)

Lewis acid (5.6)

Any species that can accept a pair of electrons and form a coordinate covalent bond

Lewis acid-base adduct (5.6)

Compound or ion that contains a coordinate covalent bond between a Lewis acid and a Lewis base

Lewis acid-base chemistry (5.6)

Reactions involving the formation of coordinate covalent bonds

Lewis base (5.6)

Any species that can donate a pair of electrons and form a coordinate covalent bond

Lewis electron dot symbol (see Lewis symbol) (9.1)

Lewis structure (9.4)

Diagram showing lone pairs and bonding pairs of electrons in a molecule or an ion

Lewis symbol (9.1)

Symbol for an element or monatomic ion that uses a dot to represent each valence electron in the element or ion

Ligand (5.6)

Molecule or ion acting as a Lewis base in complex ion formation; bonds to the central atom of the complex

Limiting reactant (1.3)

Reactant present in an amount lower than required by the reaction stoichiometry; it runs out first for a given chemical reaction and thus limits the amount of product generated

Line spectrum (8.2)

Electromagnetic radiation emitted at discrete wavelengths (i.e. contains only certain colours of light) by a specific atom (or atoms) in an excited state

Linear (9.5)

Shape in which two outside groups are placed on opposite sides of a central atom

Lipophilic (1.4)

The tendency to strongly interact with and mix well with lipids (fats/oils) and non-polar solvents

Liquid (I)

State of matter that has a definite volume but indefinite shape

Litre (L) (II)

Also called a cubic decimetre; unit of volume; 1 L = 1,000 cm³

London dispersion force (see dispersion force) (2.1)

Lone pair (9.4)

Two (a pair of) valence electrons that are not used to form a covalent bond

Magnetic dipole moment (see magnetic moment) (8.6)

Magnetic moment (8.6)

Measure of the magnetic strength and direction of a system; a vector quantity

Magnetic quantum number (m_ℓ) (8.4)

Quantum number signifying the orientation of an atomic orbital around the nucleus

Main-group element (V)

Element in groups 1, 2, and 13–18

Manometer (2.3)

Device used to measure the pressure of a gas trapped in a container

Mass (m) (I)

Fundamental property indicating amount of matter

Mass number (A) (V)

Sum of the numbers of neutrons and protons in the nucleus of an atom

Mass percentage (m/m %) (1.4)

The ratio of solute-to-solution mass expressed as a percentage

Mass-volume percent (m/v %) (1.4)

The ratio of solute mass to solution volume expressed as a percentage

Matter (I)

Anything that occupies space and has mass

Mean free path (2.7)

Average distance a molecule travels between collisions

Metal (V)

Element that is shiny, ductile, malleable, good conductor of heat and electricity; e.g. iron (Fe), copper (Cu), zinc (Zn)

Metalloid (V)

Element that conducts heat and electricity moderately well, and possesses some properties of metals and some properties of nonmetals; e.g. boron (B), silicon (Si), arsenic (As)

Method of initial rates (7.3)

Common experimental approach to determining rate laws that involves measuring the instantaneous reaction rate upon mixing the reactants

Metre (m) (II)

Standard metric and SI unit of length

Midpoint (6.3)

Point at which exactly enough acid (or base) has been added to neutralize one-half of the acid (or the base) originally present; occurs halfway to the equivalence point

Millilitre (mL) (II)

1/1,000 of a liter; equal to 1 cm³

Mixture (I)

Physical combination of more than one substance; can then be separated into its components by physical means

Molality (b) (1.4)

A concentration unit defined as the ratio of the numbers of moles of solute to the mass of the solvent in kilograms

Molar mass (M_m) (1.1)

Mass in grams of 1 mole of a substance

Molar solubility (6.4)

Solubility of a compound expressed in units of moles per liter (mol/L)

Molarity (M) (1.4)

Unit of concentration, defined as the number of moles of solute dissolved in 1 litre of solution

Mole (n) (1.1)

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; equals 6.022 × 10²³ things

Mole fraction (X) (2.5)

Ratio of the molar amount of a mixture component to the total number of moles of all mixture components

Molecular formula (1.2)

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 structure (9.4 & 9.5)

Arrangement of atoms in a molecule or ion; in VSEPR theory, it refers to a structure that includes only the placement of the atoms in the molecule

Molecularity (7.7)

Number of reactant species involved in an elementary reaction

Molecule (I)

Bonded collection of two or more atoms of the same or different elements; e.g. water (H₂O), glucose (C₆H₁₂O₆), ozone (O₃)

Monatomic ion (VI)

Ion composed of a single atom; e.g. K⁺; O^2-, Fe³⁺

Monoprotic acid (5.4)

Acid containing one ionizable hydrogen atom per molecule

Net ionic equation (1.4)

The chemical equation in which only those dissolved ionic reactants and products that undergo a chemical or physical change are represented (excludes spectator ions)

Neutral (5.2)

Describes a solution in which [H₃O⁺] = [OH⁻]

Neutralization reaction (5.5)

Reaction of an acid and a base to produce water and a salt

Neutron (IV)

Uncharged, subatomic particle located in the nucleus

Noble gas (V)

Element in group 18; e.g. helium (He), neon (Ne), krypton (Kr)

Node (8.1)

Any point of a standing wave with zero amplitude

Nomenclature (VI)

System of rules for naming objects of interest; in chemistry, a very specific system for naming compounds, in which unique substances get unique names

Nonmetal (V)

Element that appears dull, poor conductor of heat and electricity; e.g. carbon (C), phosphorus (P), sulphur (S)

Nonpolar covalent bond (see pure covalent bond) (9.3)

Nucleus (IV)

Massive, positively charged center of an atom made up of protons and neutrons

Octahedral (9.5)

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

Octet rule (9.4)

Guideline which states that 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

Open system (3.1)

System that exchanges both matter and energy with its surroundings

Orbital diagram (8.5)

Pictorial representation of the electron configuration showing each orbital as a box and each electron as an arrow

Overall reaction order (7.3)

Sum of the reaction orders for each substance represented in the rate law

Oxidant (see oxidizing agent) (1.5)

Oxidation (1.5)

Loss of one or more electrons by an atom; an increase in oxidation number

Oxidation number (1.5)

The charge each atom of an element would have in a compound if the compound were ionic

Oxidation state (see oxidation number) (1.5)

Oxidation-reduction reaction (1.5)

A chemical reaction that involves the transfer of electrons, hence it involves a change in oxidation number for one or more reactant elements

Oxidizing agent (1.5)

A substance that brings about the oxidation of another substance, and in the process becomes reduced

Oxoacid (VII)

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); e.g. HNO₃, H₂SO₄, H₃PO₄

Oxoanion (VII)

Polyatomic anion composed of a central atom bonded to oxygen atoms; e.g. sulfite (SO₃^2-), nitrate (NO₃^–), perchlorate (ClO₄^–)

p orbital (8.4)

Dumbbell-shaped region of space with high electron density, describes orbitals with ℓ = 1

Paramagnetism (8.6)

Magnetic state of substances characterized by one or more unpaired electrons; paramagnetic substances are attracted by an externally applied magnetic field

Partial pressure (2.5)

Pressure exerted by an individual gas in a mixture

Parts per billion (ppb) (1.4)

The ratio of solute-to-solution mass multiplied by 10⁹

Parts per million (ppm) (1.4)

The ratio of solute-to-solution mass multiplied by 10⁶

Pascal (Pa) (2.3)

SI unit of pressure; 1 Pa = 1 N/m²

Path function (3.3)

Function that depends on the path taken to reach that specific value

Pauli exclusion principle (8.5)

Specifies that no two electrons in an atom can have the same value for all four quantum numbers

Percent composition (1.1)

Percentage by mass of the various elements in a compound

Percent ionization (5.3)

Ratio of the concentration of ionized acid to initial acid concentration expressed as a percentage

Percent yield (1.3)

A measure of the efficiency of a reaction expressed as a percentage of the theoretical yield; actual yield divided by theoretical yield times 100% to give a percentage between 0% and 100%

Period (V)

Horizontal row of the periodic table

Periodic table (V)

Table of the elements that places elements with similar chemical properties close together

pH (5.2)

Logarithmic measure of the concentration of hydronium ions in a solution (calculated as the negative logarithm of the hydronium ion concentration)

Photon (8.1)

Smallest possible discrete packet of electromagnetic radiation, a particle of light

Physical change (I)

Change in the state or properties of matter that changes one or more of its physical properties without changing its chemical composition

Physical property (I)

Characteristic of matter that is not associated with any change in its chemical composition

Plasma (I)

Gaseous state of matter containing a large number of electrically charged atoms and/or molecules

pOH (5.2)

Logarithmic measure of the concentration of hydroxide ions in a solution (calculated as the negative logarithm of the hydroxide ion concentration)

Polar covalent bond (9.3)

Covalent bond between different atoms of different electronegativities, which cause an imbalance of electron distribution; a covalent bond with a partially positive end and a partially negative end

Polar molecule (9.5)

Molecule with an overall dipole moment

Polarizability (2.1)

Measure of the ability of a charge to distort a molecule’s charge distribution (electron cloud)

Polyatomic ion (VI)

Ion composed of more than one atom; e.g. hydroxide ion (OH^–), carbonate ion (CO₃^2-), dichromate ion (Cr₂O₇^2-)

Potential energy (E_pot) (3.1)

Energy of a particle or system of particles derived from relative position, composition, or condition

Pre-exponential factor (A) (7.5)

Proportionality constant in the Arrhenius equation, related to the relative number of collisions having an orientation capable of leading to product formation

Precipitate (6.1)

Insoluble product that forms from reaction of soluble reactants

Precipitation reaction (1.4)

A reaction that produces one or more insoluble products; when reactants are ionic compounds, sometimes called double-displacement or metathesis

Precision (III)

How closely a measurement matches the same measurement when repeated

Pressure (P) (2.3)

Force exerted per unit area

Principal quantum number (n) (8.4)

Quantum number specifying the shell an electron occupies in an atom

Product (1.2)

A substance formed by a chemical or physical change; shown on the right side of the arrow in a chemical equation

Proton (IV)

Positively charged, subatomic particle located in the nucleus

Proust’s law (see law of definite proportions) (IV)

Pure covalent bond (9.3)

Covalent bond between atoms of identical electronegativities

Pure substance (I)

Homogeneous substance that has a constant composition; types of pure substances include elements and compounds

Quantization (8.1)

Limitation of some property to specific discrete values, not continuous

Quantum mechanics (8.4)

Field of study that includes quantization of energy, wave-particle duality, and the Heisenberg uncertainty principle to describe matter

Quantum number (8.2)

Number having only specific allowed values and used to characterize the arrangement of electrons in an atom

Rare gas (see noble gas) (V)

Rate constant (k) (7.3)

Proportionality constant in a rate law specific to each reaction at a particular temperature

Rate equation (see rate law) (7.3)

Rate law (7.3)

Mathematical equation showing the dependence of reaction rate on the rate constant and the concentration of one or more reactants

Rate of diffusion (2.7)

Amount of gas diffusing through a given area over a given time

Rate of reaction (7.1)

Measure of the speed at which a chemical reaction takes place

Rate-determining step (7.7)

Slowest elementary reaction in a reaction mechanism; determines the rate of the overall reaction

Rate-limiting step (see rate-determining step) (7.7)

Reactant (1.2)

Substance undergoing a chemical or physical change; shown on the left side of the arrow in a chemical equation

Reaction coordinate diagram (7.8)

Used in chemical kinetics to illustrate the progression and various properties of a reaction

Reaction mechanism (7.7)

Stepwise sequence of elementary reactions by which a chemical change takes place

Reaction order (7.3)

Value of an exponent in a rate law (for example, zero order for 0, first order for 1, second order for 2, and so on)

Reaction profile (see reaction coordinate diagram) (7.8)

Reaction quotient (Q) (4.2)

Mathematical function describing the relative amounts of reactants and products in a reaction mixture; may be expressed in terms of concentrations (Q_c) or pressures (Q_p)

Redox reaction (see oxidation-reduction reaction) (1.5)

Reducing agent (1.5)

A substance that brings about the reduction of another substance, and in the process becomes oxidized

Reductant (see reducing agent) (1.5)

Reduction (1.5)

The gain of one or more electrons by an atom; a decrease in oxidation number

Replacement reaction (see single-displacement reaction) (1.5)

Representative element (see main-group element) (V)

Resonance (9.4)

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 (9.4)

Two or more Lewis structures that have the same arrangement of atoms but different arrangements of electrons

Resonance hybrid (9.4)

Average of the resonance forms shown by the individual Lewis structures

Reversible reaction (4.1)

Chemical reaction that can proceed in both the forward and reverse directions under given conditions

Root mean square velocity (u_rms) (2.6)

Measure of average velocity for a group of particles calculated as the square root of the average squared velocity

Rounding (III)

Procedure used to ensure that calculated results properly reflect the uncertainty in the measurements used in the calculation

s orbital (8.4)

Spherical region of space with high electron density, describes orbitals with ℓ = 0

Saturated (6.1)

Of concentration equal to solubility; containing the maximum concentration of solute possible for a given temperature and pressure

Second (s) (II)

SI unit of time

Selective precipitation (6.4)

Process in which ions are separated using differences in their solubility with a given precipitating reagent

Semimetal (see metalloid) (V)

Shell (8.4)

Atomic orbitals with the same principal quantum number, n

Shielding (8.7)

Refers to the blocking of valence shell electron attraction by the nucleus due to the presence of inner-shell electrons

SI units (International System of Units) (II)

Standards fixed by international agreement in the International System of Units (Le Système International d’Unités)

Significant digits (see significant figures) (III)

Significant figures (III)

The limit of the number of places a measurement can be properly expressed with

Single bond (9.4)

Bond in which a single pair of electrons is shared between two atoms

Single-displacement reaction (1.5)

Redox reaction involving the oxidation of an elemental substance by an ionic species; one element is substituted for another element in a compound

Solid (I)

State of matter that is rigid, has a definite shape, and has a fairly constant volume

Solubility (6.1)

Extent to which a solute may be dissolved in water, or any solvent

Solubility product constant (K_sp) (6.1)

Equilibrium constant for the dissolution of an ionic compound

Solute (1.4)

Solution component present in a concentration less than that of the solvent; minor component of a solution

Solution (see homogeneous mixture) (I)

Solvent (1.4)

Solution component present in a concentration that is higher relative to other components; the major component of a solution

Specific heat capacity (c) (3.5)

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 (1.4)

An ion that does not undergo a chemical or physical change during a reaction, but its presence is required to maintain charge neutrality

Spin quantum number (m_s) (8.4)

Number specifying the electron spin direction, either +12 or –12

Stability constant (see formation constant (K_f)) (5.6)

Standard atmosphere (atm) (2.3)

Unit of pressure; 1 atm = 101,325 Pa = 760 mmHg

Standard conditions of temperature and pressure (STP) (2.1)

273.15 K (0 °C) and 1 bar (100 kPa)

Standard enthalpy of combustion (ΔH_c°) (3.6)

Heat released when one mole of a compound undergoes complete combustion under standard conditions

Standard enthalpy of formation (ΔH_f°) (3.6)

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 molar volume (2.4)

Volume of 1 mole of gas at STP, approximately 22.7 L for gases behaving ideally

Standard state (3.4)

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 (8.1)

Localized wave phenomenon characterized by discrete wavelengths determined by the boundary conditions used to generate the waves; standing waves are inherently quantized

State function (3.3)

Property depending only on the state of a system, and not the path taken to reach that state

Stationary wave (see standing wave) (8.1)

Stepwise ionization (5.4)

Process in which a polyprotic acid is ionized by losing protons sequentially

Stoichiometric factor (1.3)

The ratio of coefficients in a balanced chemical equation, used in computations relating amounts of reactants and products

Stoichiometry (1.3)

Relationships between the amounts of reactants and products of a chemical reaction

Strong acid (5.3)

Acid that reacts completely (100% ionization) when dissolved in water to yield hydronium ions

Strong base (5.3)

Base that reacts completely (100% ionization) when dissolved in water to yield hydroxide ions

Structural formula (1.2)

Shows the atoms in a molecule and how they are connected

Subshell (8.4)

Atomic orbitals with the same values of n and ℓ

Supersaturated (6.1)

Of concentration that exceeds solubility (more than the normal maximum amount of solute in it); a nonequilibrium state

Surroundings (3.1)

All matter other than the system being studied

System (3.1)

Portion of matter undergoing a chemical or physical change being studied

Temperature (T) (3.2)

Intensive property of matter that is a quantitative measure of “hotness” and “coldness;” measure of the average amount of kinetic energy a system contains

Termolecular reaction (7.7)

Elementary reaction involving three reactant species

Tetrahedral (9.5)

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

Theoretical yield (1.3)

Amount of product that may be produced from a given amount of reactant(s) according to the reaction stoichiometry

Thermal energy (3.2)

Kinetic energy associated with the random motion of atoms and molecules

Thermochemistry (3.1)

Study of measuring the amount of heat absorbed or released during a chemical reaction or a physical change

Titrant (6.3)

Solution containing a known concentration of substance that will react with the analyte in a titration analysis

Titration curve (6.3)

Plot of some sample property (such as pH) versus volume of added titrant

Torr (2.3)

Unit of pressure; another name for a millimetre of mercury; 1 Torr = 1760 atm

Transition element (V)

Element in groups 3–12; e.g. iron (Fe), tungsten (W), silver (Ag)

Transition metal (see transition element) (V)

Transition state (‡) (see activated complex) (7.5)

Transition state theory (7.6)

Theory which says that between the state where molecules are reactants and the state where molecules are products, there is the transition state where reactants are combined in a species called the activated complex

Trigonal bipyramidal (9.5)

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 (9.5)

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 (9.4)

Bond in which three pairs of electrons are shared between two atoms

Triprotic acid (5.4)

Acid that contains three ionizable hydrogen atoms per molecule

Uncertainty (III)

Estimate of amount by which measurement differs from true value

Unified atomic mass unit (u) (V)

Alternative unit equivalent to the atomic mass unit

Unimolecular reaction (7.7)

Elementary reaction involving a single reactant species

Unit (II)

Elementary reaction involving a single reactant species

Valence electrons (8.5)

Electrons in the outermost or valence shell (highest value of n) plus any electrons in the last unfilled subshell of a ground-state atom; the electrons most likely involved in chemical reactions

Valence shell (8.5)

Outermost and highest-numbered shell of electrons in a ground-state atom

Valence shell electron-pair repulsion theory (VSEPR) (9.5)

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 (2.8)

Modified version of the ideal gas equation containing additional terms to account for non-ideal gas behavior, correcting for intermolecular forces and the volume of gas molecules

Van der Waals force (2.1)

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 Equation (4.4)

Linear relation between ln K and the standard enthalpies and entropies, describing the temperature dependence of the equilibrium constant

Vapour (2.2)

Material in the gas phase due to evaporation

Vapour pressure of water (2.5)

Pressure exerted by water vapor in equilibrium with liquid water in a closed container at a specific temperature

Vector (9.5)

Quantity having magnitude and direction

Volume (V) (II)

Amount of space occupied by an object

Volume percentage (v/v %) (1.4)

The ratio of solute-to-solution volume expressed as a percentage

Wave (8.1)

Oscillation of a property over time or space; can transport energy from one point to another

Wave-particle duality (8.1)

Observation that elementary particles can exhibit both wave-like and particle-like properties

Wavefunction (ѱ) (8.4)

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 (λ) (8.1)

Distance between two consecutive peaks or troughs (or other corresponding points) in a wave

Weak acid (5.3)

Acid that reacts only to a slight extent (less than 100% ionization) when dissolved in water to yield hydronium ions

Weak base (5.3)

Base that reacts only to a slight extent (less than 100% ionization) when dissolved in water to yield hydroxide ions

Weight (I)

Force that gravity exerts on an object

Work (w) (3.1)

Energy transfer due to changes in external, macroscopic variables such as pressure and volume; or causing matter to move against an opposing force