How is each compound represented in a chemical formula?

Answer 1

A numeral (number) written as a subscript following the chemical symbol will tell you how many atoms of that element are in the molecule being discussed. Let's take sulfuric acid as an example. It's H2SO4 as the chemist or student of chemistry writes it. There is a "sub2" following the H, so there are 2 atoms of hydrogen. There is no subscript after the S so there is only a single atom of sulfur; it's understood to be a 1 so we don't have to write it. The "sub4" after the O tells us there are 4 atoms of oxygen in this compound. Simple and easy.

Answer 2

Each compound is represented as the elements it contains in one molecule. For example, salt, or sodium chloride, is written as NaCl, because each molecule has one sodium atom and one chlorine atom. Carbon Dioxide is similarly written as CO2 because every molecule has one C (carbon) atom and two O (oxygen) atoms.