Answer is: (4) NH4Cl.
Name of this chemical copmpound is ammonium chloride.
Ammonium chloride (NH₄Cl) is chemical compound with neutral charge.
1) Hydrogen (H) has oxidation number +1 in compounds with nonmetals (nitrogen and chlorine).
2) Chlorine has oxidation number -1, because ammonium ion (NH₄⁺) has positive charge.
3) In ammonium cation (NH₄⁺), nitrogen has higher electronegativity than hydrogen, so it has negative oxidation number -3:
x + 4 · (+1) = +1.
x = 1 - 4.
x = -3; oxidation number of nitrogen.
Electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons towards itself.
Other molecules have covalent chemical bonds.