Which substance is a molecule?

1. Ch4

2. NaF

3. Ar

4. Pb

Molecules are substances that contain two or more elements, if these elements are different, then the substance is also a compound.

However, considering only the definition of a molecule, it is evident that both CH4 and NaF are molecules as they contain more than one element.

In fact, all of these (Ch4, NaF, Ar, and Pb) are molecules.