Question

How do you determine the oxidation number of nitrogen in the nitrate ion?

Answer 1

Hint: The answer here is dependent on the fact that oxygen has the oxidation number of -2 usually but except in the peroxide form where it has -1 and the sum of all these oxidation numbers is the charge on the ion which is given as, Oxidation number = oxidation number of the remaining atoms $+x$= total charge on the ion. This formula gives the required answer.

Complete answer:
We have studied about the various calculations in the inorganic part of chemistry which also include the calculation of the oxidation number of the central atom with the known oxidation number of the atoms to which the central atom is attached to.
Let us now recall these formulas so that we can deduce the required answer.
- Oxidation state or also called as the oxidation state of an atom is defined as the degree of oxidation that is the loss or gain of electrons of an atom in the compound or ion.
- Based on this definition we can calculate the oxidation state of the central atom which is given as,
Oxidation number = oxidation number of the remaining atoms $+x$= total charge on the ion
where, x is the charge on the central atom to be found.
Now, for the nitrate ion which is the formula $N{{O}_{3}}^{-}$, the total charge on the ion is -1 and that of oxygen on this is -2. Oxidation state of oxygen in peroxide will be -1 which is an exceptional case.
Here there are three oxygen atoms thus the total charge will be $-2\times 3=-6$
Now, the oxidation number thus is calculated by using the above formula which will be,
Oxidation number = $x+(-6)=-1$
\[\Rightarrow x=-1+6=+5\]
Therefore, the oxidation number of nitrogen in nitrate ion is \[+5\]

Note:
To find the oxidation state of any molecule or ion, you should be thorough with the formula of the given name of the compound and also the total charge on that ion and also about the oxidation numbers of some basic elements.