Question

Why are some molecules diatomic?

Answer 1

To a first approximation all elements are diatomic....

Explanation:

How so? Well, because hydrogen is by far the most abundant element in the universe as far as we know...and commonly hydrogen appears as the `H_2` molecule...

And this occurrence owes to thermodynamic stability...the formation of hydrogen-hydrogen bonds is exothermic...

`dotH + dotH rarr H-H+Delta`

All elemental gases (well the ones with any chemistry) are also diatomic...`H_2, Li_2, C_2, N_2, O_2, X_2`...the elements are thermodynamically MORE stable as the diatom...