The cation is written first in the chemical formula for a binary ionic compound.
SO2 is the chemical formula of sulfur dioxide.
The anion.
NH3 is the chemical formula of ammonia.
Ba3N2
There is no 'binary formula'. You can say that hydrogen iodide is a binary compound, that is one formed from just two elements. HI is its formula.
Lithium selenide
The chemical formula KCl is for potassium chloride.
The formula for the binary ionic compound sodium nitride is Na3N.
Binary compound: a chemical compound with only two types of atoms; examples: NaCl, HCl, CaS, H2O.
A binary compound is a chemical compound that contains exactly two different elements. O2 has one, so its not a binary compound.
I'm not sure what a "type 2 binary compound" means, but the other conditions of the question are satisfied by sodium oxide, with formula Na2O.
A binary compound is formed from two different chemical elements.