Anode
The electrode at which oxidation occurs. Compare to cathode.
Aqueous solution
A solution in which water is the solvent.
Aromatic compounds
Planar, cyclic organic compounds that are unusually stable because of the delocalization of π
electrons.
Arrhenius acid
A species that donates protons (H+) in an aqueous solution; e.g., HCl.
Arrhenius base
A species that gives off hydroxide ions (OH–) in an aqueous solution; e.g., NaOH.
Atom
The most elementary form of an element; it cannot be further broken down by chemical means.
Atomic mass
The averaged mass of the atoms of an element, taking into account the relative abundance of the
various isotopes in a naturally occurring substance. Also called the atomic weight.
Atomic mass units (amu)
A unit of mass defined as the mass of a carbon-12 atom; approximately equal to the mass of one
proton or one neutron.
Atomic number