Here's why:

* Molecule: A molecule is formed when two or more atoms bond together.

* Atoms: The basic building blocks of matter.

Examples:

* Water (H₂O): Composed of 2 hydrogen atoms and 1 oxygen atom (3 atoms total).

* Oxygen (O₂): Composed of 2 oxygen atoms.

* Carbon dioxide (CO₂): Composed of 1 carbon atom and 2 oxygen atoms (3 atoms total).

So, there's no fixed number of atoms in a molecule. It depends on the specific molecule and the elements it's composed of.