Question

Which of the following are appropriate oxidation states exhibited by the elements belonging to the group 15 family?

• A. 3
• B. -3
• C. 5
• D. All of these

Answer 1

The correct option is D All of these

We have encountered the anomalous behavior of Nitrogen among the group 15 elements. If you took the hint, it is obvious that +3 and +5 oxidation states are the recurring theme among group 15 elements. Let us try and answer this question purely from what we know already, shall we?
We know that both Lithium and Magnesium form nitrides when they are burnt in air.
$3Mg+N_2\to M{g}_3{N}_2$
Sodium also forms a Nitride - $N{a}_{3}N$
Here, the nitride ion is $N^{3-}$. Let us take $M{g}_3{N}_2$. Alkaline earth metal exists as $M{g}^{2+}$ ions. We know that in ionic alkaline earth metal compounds, they tend to have +2 oxidation state. Let the oxidation state of Nitrogen be y.
Overall the molecule is neutral, so we have
3(+2) + 2(y) = 0
Solving, the oxidation state of N atom in Magnesium Nitride is y = -3.
Hence the option D is the most appropriate!