Which oxidation state for nitrogen is correctly given?
a) Compound - \[N{{H}_{3}}\], oxidation: +3
b) Compound- \[\left[ Co{{(N{{H}_{3}})}_{5}}Cl \right]\], oxidation: +1
c) Compound - \[M{{g}_{3}}{{N}_{2}}\], oxidation: —3
d) Compound- \[N{{H}_{2}}OH\], Oxidation: +1

Hint: An oxidation state is a number that is assigned to an element in a chemical combination. This number represents the number of electrons that an atom can gain, lose, or share when chemically bonding with an atom of another element. The oxidation number for mono-atomic ions always has the same value as the net charge corresponding to the ion.

Complete answer:
In the given compound \[N{{H}_{3}}\], we have to find the oxidation state of nitrogen,
The oxidation state of hydrogen is +1.
Let us assume the oxidation state of nitrogen to be x.
x + 1 × (3) = 0
x = -3
Similarly, in \[\left[ Co{{(N{{H}_{3}})}_{5}}Cl \right]\], in a complex the oxidation state of \[N{{H}_{3}}\] is zero. Therefore, the oxidation state of Nitrogen is zero here.
In \[M{{g}_{3}}{{N}_{2}}\],
The oxidation state of magnesium is +2.
Let us assume the oxidation state of nitrogen to be x.
3 × (+2) + 2x = 0
+6 +2x = 0
2x = -6
x = -3
Similarly, in \[N{{H}_{2}}OH\]
The oxidation state of hydrogen is +1.
The oxidation state of oxygen is -2.
Let us assume the oxidation state of nitrogen to be x.
x + 3 × (+1) + (-2) + (+1) = 0
x + 3 -2 +1 = 0
x + 2 = 0
x = -2



Therefore, the correct option is (c).

Note: Generally, in nitrogen compounds, the oxidation states exhibited by nitrogen ranges from -3 (minimum), in ammonia and amines, to +5 (maximum), in nitric acid. Oxidation state of +3 are more commonly occurring as it requires less energy