What is the atomic number of a diatomic elemental molecule?

Question

This question was on a chem quiz today and I'm not completely sure if its a trick question.

Answer 1

I interpret the question to mean that you are supposed to identify one of the 8 or 9 elements which exist as diatomic molecules. They are the two elements in air, the halogens and hydrogen.

Answer 2

Elemental Molecule

Answer 3

1