Question

Which list of formulas represents only compounds? H2, N2, O2 H2, Ne, NaCl CO2, H2O, NH3 MgO, NaCl, O2

Answer 1

A compound has to have at least two different elements in
(1) is the only list in which each of the three symbols representations show at least two different elements

Answer 2

The list that represents only compounds are CO2, H2O, and NH3