Chemical Formula

Imagine you’re making a salad dressing that requires mixing three parts oil with one part vinegar. Similarly, chemical compounds are formed by a combination of elements in fixed ratios, represented by chemical formulas.

These formulas use symbols to show the element and subscripts to show the number of atoms of the elements in a molecule. For example, water, H₂O has one oxygen and two hydrogen atoms.

Chemical formulas follow specific rules. For example, lets consider table salt, it comprises one sodium atom paired with one chlorine atom.

This is an ionic compound, and for such compounds, the chemical formula comprises the positive ion symbol written first, followed by the negative ion.

Now consider carbon dioxide, the gas we exhale. It's a covalent compound in which one carbon atom shares bonds with two oxygen atoms.

In the chemical formula of such compounds, the element farther left in the periodic table is written first, followed by the element at the right. As there are two oxygen atoms, the subscript 2 is written after “O.”