Vocabulary

absolute temperature scale

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

absolute zero

Theoretically the lowest attainable temperature.

acceptor impurity

An impurity that can accept electrons from a semiconductor.

accuracy

The closeness of a measurement to the true value of the quantity that is measured.

acid

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

acid ionization constant (Ka)

The equilibrium constant for the acid ionization.

actinoid series

Elements that have incompletely filled 5f subshells or readily give rise to cations that have incompletely filled 5f subshells.

activated complex

The species temporarily formed by the reactant molecules as a result of the collision before they form the product.

activation energy (Ea)

The minimum amount of energy required to initiate a chemical reaction.

activity series

A summary of the results of many possible displacement reactions.

actual yield

The amount of product actually obtained in a reaction.

addition reaction

A reaction in which one molecule adds to another.

adhesion

Attraction between unlike molecules.

alcohol

An organic compound containing the hydroxyl group —OH.

aldehydes

Compounds with a carbonyl functional group and the general formula RCHO.

aliphatic hydrocarbons

Hydrocarbons that do not contain the benzene group or ring.

alkali metals

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

alkaline earth metals

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

alkanes

Hydrocarbons having the general formula CnH2n+2.

alkenes

Hydrocarbons that contain one or more carbon-carbon double bonds.

alkynes

Hydrocarbons that contain one or more carbon-carbon triple bonds.

allotropes

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

alloy

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

alpha (α) rays

Helium ions with a positive charge of +2.

alpha decay

A radioactive process in which an alpha particle is emitted from a nucleus.

alpha particles

See alpha rays.

amalgam

An alloy of mercury with another metal or metals.

amines

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

amino acids

Compounds that contain at least one amino group and at least one carboxyl group.

amorphous solid

A solid that lacks a regular three-dimensional arrangement of atoms or molecules.

amphoteric oxide

An oxide that exhibits both acidic and basic properties.

amplitude

The vertical distance from the middle of a wave to the peak or trough.

anion

An ion with a net negative charge.

anode

The electrode at which oxidation occurs.

antibonding molecular orbital

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

aqueous solution

A solution in which the solvent is water.

aromatic hydrocarbon

A hydrocarbon that contains one or more benzene rings.

atmospheric pressure

The pressure exerted by Earth’s atmosphere.

atom

The basic unit of an element that can enter into chemical combination.

atom economy

A measure of the overall efficiency of converting reactants into useful products.

atomic mass

The mass of an atom in atomic mass units.

atomic mass unit (amu)

A mass exactly equal to the mass of one carbon-12 atom.

atomic number (Z)

The number of protons in the nucleus of an atom.

atomic orbital

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

atomic radius

One-half the distance between the two nuclei in two adjacent atoms of the same element.

Aufbau principle

As protons are added to the nucleus, electrons similarly are added to the atomic orbitals.

Avogadro’s law

At constant pressure and temperature, the volume of a gas is directly proportional to the number of moles of the gas.

Avogadro’s number (NA)

6.022 × 1023; the number of particles in a mole.

band theory

Delocalized electrons move freely through 'bands' formed by overlapping molecular orbitals.

barometer

An instrument that measures atmospheric pressure.

base

A substance that yields hydroxide ions (OH−) when dissolved in water.

base ionization constant (Kb)

The equilibrium constant for the base ionization.

battery

A galvanic cell, or a series of combined galvanic cells, used as a source of direct electric current.

beta (β) rays

Electrons.

beta particles

See beta rays.

bimolecular reaction

An elementary step that involves two molecules.

binary compounds

Compounds formed from just two elements.

boiling point

The temperature at which the vapor pressure of a liquid is equal to the external atmospheric pressure.

boiling-point elevation (ΔTb)

The boiling point of the solution minus the boiling point of the pure solvent.

bond enthalpy

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

bond length

The distance between the nuclei of two bonded atoms in a molecule.

bond order

The difference between the numbers of electrons in bonding and antibonding molecular orbitals, divided by two.

bonding molecular orbital

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

Born-Haber cycle

The cycle that relates lattice energies of ionic compounds to various thermodynamic quantities.

boundary surface diagram

Diagram of the region containing a substantial amount of the electron density in an orbital.

Boyle’s law

The volume of a fixed amount of gas maintained at constant temperature is inversely proportional to the gas pressure.

breeder reactor

A nuclear reactor that produces more fissionable materials than it uses.

Brønsted acid

A substance capable of donating a proton.

Brønsted base

A substance capable of accepting a proton.

buffer solution

A solution of a weak acid or base and its salt that resists changes in pH.

calorimetry

The measurement of heat changes.

carbides

Ionic compounds containing the C4− ion.

carboxylic acids

Acids that contain the carboxyl group —COOH.

catalyst

A substance that increases the rate of a chemical reaction without being consumed.

catenation

The ability of atoms to form bonds with one another.

cathode

The electrode at which reduction occurs.

cation

An ion with a net positive charge.

cell voltage

Difference in electrical potential between the anode and the cathode of a galvanic cell.

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.

Charles’s law

The volume of a fixed amount of gas maintained at constant pressure is directly proportional to the absolute temperature.

chelating agent

A substance that forms complex ions with metal ions in solution.

chemical energy

Energy stored within the structural units of chemical substances.

chemical equation

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

chemical equilibrium

A state in which the rates of the forward and reverse reactions are equal.

chemical formula

An expression showing the chemical composition of a compound.

chemical kinetics

The area of chemistry concerned with the rates at which chemical reactions occur.

chemical property

Any property of a substance that cannot be studied without converting the substance into something else.

chemical reaction

A process in which a substance is changed into one or more new substances.

chemistry

The study of matter and the changes it undergoes.

chiral

Compounds or ions that are not superimposable with their mirror images.

chlor-alkali process

The production of chlorine gas by the electrolysis of aqueous NaCl solution.

closed system

A system that enables the exchange of energy but not mass with its surroundings.

closest packing

The most efficient arrangements for packing atoms, molecules, or ions in a crystal.

cohesion

The intermolecular attraction between like molecules.

colligative properties

Properties of solutions that depend on the number of solute particles in solution.

colloid

A dispersion of particles of one substance throughout another.

combination reaction

A reaction in which two or more substances combine to form a single product.

combustion reaction

A reaction in which a substance reacts with oxygen to produce heat and light.

common ion effect

The shift in equilibrium caused by adding a compound with an ion in common.

complex ion

An ion containing a central metal cation bonded to one or more molecules or ions.