Which substances in the simulation have particles that are only atoms?

All matter is made of particles; these can be single atoms or atoms chemically joined to make molecules. Using this fact, matter can be classified into three broad groups: elements, compounds and mixtures. In an element, all the atoms are of the same type. If more than one type of atom is chemically joined, then a compound has been formed. If more than one type of atom or molecule is contained in the same substance, and the particles aren't chemically joined, this is a mixture.

In the simulation, neon and argon have particles that are single atoms. On the other hand, each particle of oxygen is made of two atoms of the same kind.

Hope this helps :)

seeing the graph would