Writing formulas for molecular compounds

It is important to remember that the prefix indicates number of atoms, no the charge. So, molecular compounds do not use the crisscross rule.

Steps:

-         Write the symbol of the elements

-         Write the subscript for the number of atoms represented by the prefix.

Examples:

Sulphure trioxide – SO₃

Diphosphorus pentasulphide – P₂S₅

Carbon dioxide – CO₂