Explore the Chemical Formulae of Compounds

Ethanol, steric acid, methanol...... all names of compounds.

Each compound has a unique chemical formula. It is made up of symbols and numbers. The symbols tell us which elements are in the compound, and the numbers tell us how many atoms of each element are in a molecule of the compound. 

Carbon dioxide has the formula:

CO₂

This means there is 1 atom of carbon and 2 atoms of oxygen in each molecule of carbon dioxide.

We can apply the same principle to more complex compounds, but don't let the complexity get you confused!

MgSO₄ contains three elements, Mg (magnesium), S (sulfur) and O (oxygen). The numbers tell us how many of each atom there are in a molecule of the compound, so in this case, as there is no number after Mg, we can tell there is only 1 atom present. The same goes for S. But there is a little 4 after O, so that tells us that there are 4 atoms of oxygen in a molecule of the compound.

By the way, the word 'formulae' is the plural of the word formula. If we're talking about more than one formula, we usually say formulae.

Let's have a go at some questions now.