Oxidation number of Nitrogen

Question: Arrange the following compounds to the decreasing order of the oxidation state of Nitrogen.

NO, HNO₃, NH₄Cl, N₂

Solution: Let us recall some basic rule of oxidation number.

• The sum of the oxidation number of all the atoms in a neutral compound is zero.
• The oxidation number of a free element is always zero. Like the atoms in He and N₂ have oxidation numbers of 0.           
• The usual oxidation number of hydrogen is +1.
• The oxidation number of Chlorine is -1.
• The oxidation number of oxygen is usually -2.

Now find out the oxidation state of nitrogen in the given compounds.

Oxidation state of N in NO:  

Oxidation state of N in HNO₃ :

Oxidation state of N in NH₄Cl : 

Oxidation state of N in N₂ : As we know the oxidation number of a free element is always zero. Thus

According to above calculation, compounds in decreasing order of oxidation state are: