Question

Name diatonic elements

Answer 1

I assume you mean diatomic elements.
Those are hydrogen, oxygen, nitrogen, fluorine, chlorine, bromine, and iodine. They all exist in the form $X_{2}$ ($H_{2}, O_{2} , N_{2} , F_{2} , Cl_{2} , Br_{2} , I_{2}$). Where they are all bonded to another one of themselves (a hydrogen atom binds to another hydrogen atom, a fluorine atom binds to another fluorine atom, etc.)

Answer 2

Hydrogen, oxygen, nirtogren, fluorine, chlorine, bromine, iodine