A carbon dioxide molecule has one carbon atom and two oxygen atoms.The carbon means 1 carbon. The Di-oxide means 2 oxygen. Di (as in dos which is 2 in spanish) means 2. Oxide means oxygen.
The empirical formula for carbon dioxide is CO2 (that 2 is supposed to be small...). So, there are two atoms of oxygen in one carbon dioxide molecule (there is also a clue in the name: "di" can...