Question

Oxidation state of N is given correct in:
(A) $ 0 $ in $ [Co{{(N{{H}_{3}})}_{5}}Cl]Cl $
(B) $ -1 $ in $ N{{H}_{4}}OH $
(C) $ -3 $ in $ {{({{N}_{2}}{{H}_{5}})}_{2}}S{{O}_{4}} $
(D) $ -3 $ in $ M{{g}_{3}}{{N}_{2}} $

Answer 1

Hint : Oxidation state or also called as oxidation number is the number of electrons needed by an atom or lost by an atom to form chemical bonds with the other atom. It can be negative or positive depending upon whether an electron is taken or lost.

Complete Step By Step Answer:
The term oxidation was initially used to show the reaction with oxygen.
Oxidation state shows whether the atom has gained, lost or shared the electrons. For example, in iron ion $ F{{e}^{3+}} $ has an oxidation number of $ +3 $ since it can gain three electrons to form a bond with oxygen ion $ {{O}^{2-}} $ having an oxidation number of $ -2 $ since it can donate two electrons to form bond.
Some elements have the same oxidation number in different compounds like fluorine having $ -1 $ oxidation state in all compounds while nitrogen have different oxidation states in different compounds like $ -3 $ in ammonia and $ +5 $ in nitric acid.
The minimum or lowest oxidation state of an element is the one below which an element cannot exist. The oxidation state of uncombined elements is zero because they have not been oxidized or reduced.
Oxidation state of N is in
 $ [Co{{(N{{H}_{3}})}_{5}}Cl]Cl $ is $ -3 $
 $ N{{H}_{4}}OH $ is $ -3 $
 $ {{({{N}_{2}}{{H}_{5}})}_{2}}S{{O}_{4}} $ is $ -2 $
 $ M{{g}_{3}}{{N}_{2}} $ is $ -3 $
So, the correct option is D.

Note :
In a compound oxidation state is equal to the sum of total charges of the compound or ion. An element in its free form has oxidation state zero. The oxidation state is the difference between the number of electrons associated with an atom in a compound.