Question

Are all molecules = made up of two different atoms?

Answer 1

No. Multiple atoms of a single element can sometimes form molecules.

Explanation:

It's most often diatomic molecules of an element like `"H"_2` for hydrogen, `"N"_2` for nitrogen, or `"O"_2` for oxygen. But sometimes a single element can form molecules with more atoms, like `"O"_3` for ozone (another molecular form of oxygen) or `"S"_8` for sulfur. Single atoms of noble gases like atgon (`"Ar"`) may also be considered as molecules.