∞ generated and posted on 2016.01.01 ∞
Chemically pure substance that consists of two or more atoms associated in a fixed ratio by one or more chemical bonds.
Compounds include molecules and salts, and can include ions. Biologically important compounds include macromolecules, coenzymes, and various organic subunits but see also hydrocarbons.
Also compounds though not necessarily appreciated as such are water, molecular oxygen, carbon dioxide, and various other substances that familiarly exist as gasses and other fluids rather than as solids.
Interestingly, metals, particularly elementary pure metals, are not compounds to the extent that that they do not consist of fixed ratios of atoms, that is, just as helium gas is not a compound nor elementary sulfur.