Which of these are a binary ionic compound?

Question

O2
NaF
H2SO4
Cu(No3)2

Answer 1

A binary molecule is one made up of only two atoms. That leaves O2 and NaF. H2SO4 has 7 and Cu(NO3)2 has 9.

An ionic compound has different atoms, one with + charge and one with - charge (and the charges balance out). Since O2 is composed of two of the same atom, that leaves NaF - Sodium Fluoride.