His 'atomic theory' was developed from his studies of gases. Challenge Question 2. All matter is made up of atoms that are most commonly arranged in clusters called molecules. Oxygen is a gas. Each molecule of oxygen has the chemical formula O 2 which means that it is made up of two oxygen atoms.
Carbon dioxide is also a gas.
Each molecule of carbon dioxide has the chemical formula CO 2 which means that it is made up of one atom of carbon and two atoms of oxygen. Names of those who sent correct responses Question 1. LisaLeo, Dave N., Andrew, Jester, Manda, Katie F. Question 2.