acid: a compound that yields H+ ions in solution or a solution in which the concentration of H+ exceeding OH-.
acid ionization constant: the equilibrium constant describing the degree of ionization of an acid.
actinides: the row of elements below the periodic table, from thorium to lawrencium.
alkali: synonym for base.
alkali metals: the column of elements from lithium to francium.
alkaline earths: the column of elements from beryllium to radium.
alkane: a hydrocarbon without a double bond, triple bond, or ring structure.
alkene: a hydrocarbon with one or more double bonds and no triple bond.
alkyne: a hydrocarbon with one or more triple bonds.
alpha particle: a cluster of 2 protons and 2 neutrons emitted from a nucleus in one type of radioactivity.
anion: a chemical species with a negative charge.
anode: the negative electrode at which oxidation occurs.
aqueous: refers to a solution with water as solvent.
aromatic: refers to an organic compound with a benzene-like ring.
atom: the smallest amount of an element; a nucleus surrounded by electrons.
atomic number: the number of protons in the nucleus of the chemical element.
atomic weight: the weight in grams of one mole of the chemical element; approximately the number of protons and neutrons in the nucleus.
Avogadro's law: equal volumes of gases at the same temperature and pressure that contain the same number of molecules.
Avogadro's number: 6.02 x 1023, the number of molecules in 1 mole of a substance.
base: a compound that yields OH- ions in solution or a solution in which the concentration of OH- exceeds H+.
beta particle: an electron emitted from a nucleus in one type of radioactivity.
boiling point: the temperature at which a liquid changes to a gas.
boiling point elevation: an increase in the boiling point of a solution, proportional to the concentration of solute particles.
Boyle's law: the volume of a gas varies inversely with pressure.
calorie: a unit of energy, equal to 4.184 joules.
catalyst: a substance that accelerates a chemical reaction without itself being consumed.
cathode: the electrode at which reduction occurs.
cation: an atom or molecule with a positive charge.
Charles' law: the volume of a gas varies directly with absolute temperature.
chemical equation: a shorthand way of describing a chemical change using symbols of elements and formulas of compounds.
chemical formula: a representation of a compound to show its composition using symbols and subscript numbers.
compound: a substance formed by the chemical combination of two or more elements.
concentration: the relative abundance of a solute in a solution.
congeners: elements with similar properties, arranged in columns of the periodic table.
conjugate: an acid and base that are related by removing or adding a single hydrogen ion.
covalent bond: atoms linked together by sharing valence electrons.
critical point: a point in a phase diagram where the liquid and gas states cease to be distinct.
crystalline: the regular, geometric arrangement of atoms in a solid.
decomposition: a chemical reaction in which a compound is broken down into simpler compounds or elements.
dissociation: the separation of a solute into constituent ions.
electrochemical: cell a device that uses a chemical reaction to produce an electric current.
electrode: the point in an electrochemical cell at which reduction or oxidation occurs.
electrolysis: the decomposition of a substance by an electric current.
electrolyte: a substance that forms ions when dissolved in water.
electromotive: force: the electrical potential produced by a chemical reaction voltage.
electron: a light subatomic particle with negative charge; found in orbitals surrounding an atomic nucleus.
electronegativity: a number describing the attraction of an element for electrons in a chemical bond.
element: a substance that cannot be decomposed; each chemical element is characterized by the number of protons in the nucleus.
EMF: See electromotive force.
endothermic: refers to a reaction that requires heat.
energy: the concept of motion or heat required to do work.
enthalpy: the thermodynamic quantity measuring the heat of a substance.
entropy: the thermodynamic quantity measuring the disorder of a substance.
equilibrium: a balanced condition resulting from two opposing reactions.
equilibrium: constant the ratio of concentrations of products to reactants for a reaction at chemical equilibrium.
exothermic: refers to a reaction that releases heat.
faraday: a unit of electric charge equal to that on 1 mole of electrons.
Faraday's laws: two laws of electrolysis relating the amount of substance to the quantity of electric charge.
fluid: a liquid or gas.
free energy: the thermodynamic quantity measuring the tendency of a reaction to proceed; also called Gibbs free energy.
freezing point: the temperature at which a liquid changes to a solid.
freezing point depression: the decrease in freezing point of a solution, proportional to the concentration of solute particles.
fusion: melting.
gas: a state of matter in which molecules are widely separated, fluid, expandable, and compressible.
gas constant: R equals 0.082 liter-atmospheres per mole-degree.
gram formula: weight an amount of a substance equal in grams to the sum of the atomic weights.
ground state: the electronic configuration of lowest energy for an atom.
group: a column of elements in the periodic table.
half-reaction: an oxidation or reduction reaction with free electrons as a product or reactant.
halogens: the column of elements from fluorine to astatine.
heat: a form of energy that spontaneously flows from a warm body to a cold body.
heat capacity: the amount of energy needed to raise the temperature of a substance by one degree Celsius.
hydrocarbon: an organic compound containing only carbon and hydrogen.
hydrogen bond: a weak, secondary bond between a partially positive hydrogen atom and a partially negative N, O, or F atom. An inter-molecular force of attraction.
hydroxide: refers to the OH- ion.
ideal gas equation: the equation relating the volume of a gas to its pressure, temperature and moles of gas.
inert gases: the column of elements from helium to radon; also called noble gases.
ion: an atom with an electric charge due to gain or loss of electrons.
ionic bond: atoms linked together by the attraction of unlike charges.
ionization: adding or subtracting electrons from an atom; alternatively, the dissociation of a solute into ions.
isoelectronic: refers to several dissimilar atoms or ions with identical electronic configurations.
isomers: several molecules with the same composition but different structures.
isotope: a variety of an element characterized by a specific number of neutrons in the nucleus.
joule: a unit of energy equal to 0.239 calorie.
lanthanides: the row of elements beneath the periodic table, from cerium to lutetium; also called rare earths.
Le Chatelier's principle: a system that in equilibrium is disturbed adjusts so as to minimize the disturbance.
liquid: a state of matter in which the molecules are touching, fluid, incompressible.
litmus: an indicator that turns red in acid and blue in alkaline solution.
melting point: the temperature at which a solid changes to a liquid.
metallic bond: atoms linked together by the migration of electrons from atom to atom.
metals: the elements in the middle and left parts of the periodic table, except for hydrogen.
molality: the number of moles of solute in 1 kilogram of solvent.
molarity: the number of moles of solute in 1 liter of solution.
molar heat capacity: the amount of heat required to raise the temperature of 1 mole of substance 1 degree Celsius.
mole: an amount of a substance equal in grams to the sum of the atomic weights.
mole fraction: the fraction of moles (or molecules) of one substance in the total moles (or molecules) of all substances in the mixture. If the mole fraction of substance A is 0.1, one-tenth of all the molecules in a mixture are A molecules.
molecular formula: describes the ratio of elements in a molecule.
molecule: a group of atoms linked together by covalent bonds.
neutralization: the chemical reaction of an acid and base to yield a salt and water.
neutron: a heavy subatomic particle with zero charge; found in an atomic nucleus.
noble gases: the column of elements from helium to radon; also called inert gases.
nonmetals: the elements in the upper right part of the periodic table, and also hydrogen.
nucleon: a proton or neutron found in an atomic nucleus.
nucleus: the core of an atom, containing protons and neutrons.
orbital: a component of a subshell occupied by up to 2 electrons.
organic: refers to compounds based on carbon.
organic chemistry: an area of chemistry dealing principally with the chemistry of carbon.
oxidation: the loss of electrons by a species.
oxidation number: a signed integer representing the real or hypothetical charge on an atom.
oxide: a compound of oxygen and another element.
period: a horizontal row of elements in the periodic table.
periodic table display: of the elements in order of atomic number with similar elements falling into columns.
pH: a number describing the concentration of hydrogen ions in a solution. Equals -log[H+].
phase: a substance with uniform composition and definite physical state.
polar bond: a bond with both ionic and covalent characteristics.
polyprotic: refers to an acid with several hydrogens that can ionize.
precipitate: a solid that separates from solution.
product: a substance on the right side of a chemical reaction.
proton: a heavy subatomic particle with a positive charge; found in an atomic nucleus.
radioactivity: the emission of subatomic particles from a nucleus.
rare earths: the elements from cerium to lutetium; lanthanides.
reactant: a substance on the left side of a chemical reaction.
redox: refers to a reaction in which simultaneous reduction and oxidation occur.
reduction: the gain of electrons by a species.
salt: a solid compound composed of both metallic and nonmetallic elements, often as ions.
saturated: describes a solution that holds as much solute as possible.
shell: a set of electron orbitals with the same principal quantum number.
solid: a state of matter in which the molecules are touching and possessing rigid shape and is not compressible.
solubility: the upper limit of concentration of a solute.
solubility product: the constant obtained by multiplying the ion concentrations in a saturated solution.
solute: the substance that is dissolved in a solution.
solution: a homogeneous mixture consisting of a solvent and one or more solutes.
solvent: the host substance of dominant abundance in a solution.
specific heat capacity: the amount of heat required to raise 1 gram of a substance 1 degree Celsius.
standard temperature and pressure: 0° and 1 atmosphere.
states of matter: solid, liquid, and gas.
stoichiometric: refers to compounds or reactions in which the components are in fixed, whole-number ratios.
STP: See standard temperature and pressure.
strong electrolyte: an acid, base, or salt that dissociates almost completely to ions in aqueous solution.
structural formula: depicts the bonding of atoms in a molecule.
sublimation: the transformation of a solid directly to a gas without an intervening liquid state.
subshell: a set of electron orbitals with the same principal and second quantum number; for example, 2p, 3s, and so on.
symbol: an abbreviation for the name of an element; for example, C for carbon.
transition metals: the three rows of elements in the middle of the periodic table, from scandium to mercury.
triple point: a point in a phase diagram where the three states of matter are in equilibrium.
valence: a signed integer describing the combining power of an atom.
valence electrons: the outermost shell of electrons in an atom or ion.
weak electrolyte: an acid, base, or salt that dissociates only slightly to form ions in solution.
