When nitrogen and aluminum form an ionic bond, the formula of the ionic compound is AlN. Aluminum forms a cation Al⁺³ and nitrogen forms an anion N⁻³. When each cation of Al⁺³ combines with an anion of N⁻³, AlN or aluminum nitride is formed
You can automatically rule out CH₄ since it has no lone pairs at all around the central atom. Water has 2. Ammonia is the only Lewis structure that contains one lone pair.
