elements that exist as molecule
Oxygen would be (O2). The 2 is a subscript. Sub means below. The 2 is written to the right of and below the O. A pair of oxygen atoms is a molecule of oxygen. A molecule is the smallest particle of a substance that exists independently. Molecules of most elements are made up of only one of atom of that element. Oxygen, along with nitrogen, hydrogen, and chlorine are made up of two atoms. Look at the model of oxygen above.