Question

which substance is a molecule?
1. Ch4
2. NaF
3.Ar
4. Pb

Answer 1

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.

Answer 2

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