4. INORGANIC MOLECULES AND COMPOUNDS

4. INORGANIC MOLECULES AND COMPOUNDS

Simple diatomic molecules of a single element are designated by the symbol for the element with a subscript 2. That indicates that the element contains 2 atoms. Thus the hydrogen molecule is H₂; the nitrogen molecule, N₂; and the oxygen molecule, O₂. Polyatomic molecules of a single element are designated by the symbol for the element with a numerical subscript corresponding to the number of atoms in the molecule. Examples are the phosphorus molecule, P₄, and the sulphur molecule, S₈.

Diatomic covalent molecules, containing unlike elements, have a similar designation. The formula for hydrogen chloride is HCl. The more electropositive element is always designated first in the formula.

For polyatomic covalent molecules containing unlike elements, numerical subscriptions are used to designate the number of atoms of each element present in the molecule, for example, water, H₂O. Again, as in diatomic molecules, the more electropositive element is placed first in the formula.