# What are chemical formulas and the role of subscripts in them?

Apr 24, 2014

Chemical formulas are the chemists short hand for molecules.

Instead of writing out the words Magnesium Chloride the chemist simply uses the formula $M g C {l}_{2}$.

The formula $M g C {l}_{2}$ informs us that this molecule has one atom of Magnesium and two atoms of Chlorine. The subscript tells us the number of atoms in the molecule. The subscript one is never used.

For the molecule Calcium Phosphate the chemist writes $C {a}_{3} {\left(P {O}_{4}\right)}_{2}$

This formula tells us that there are 3 atoms of Calcium attached to 2 molecules of the polyatomic ion phosphate which has 1 Phosphorus attached to 4 oxygen atoms.