What is the oxidation number of nitrogen in the nitrate ion?

1 Answer
Nov 4, 2015

+5

Explanation:

Here are some of the rules for solving oxidation state of any element:

(1) The total charge of a stable compound is always equal to zero (meaning no charge).

For example, the H2O molecule exists as a neutrally charged substance.

(2) If the substance is an ion (either there is a positive or negative charge) the total oxidation state of the ion is the charge (i.e. oxidation state of NO-13 ion is -1).

(3) All elements from Group 1A has an oxidation state of +1 (e.g. Na+1, Li+1). All Group 2A and 3A elements have an oxidation state of +2 and +3, respectively. (e.g. Ca2+, Mg2+, Al3+)

(4) Oxygen always have a charge -2 except for peroxide ion (O2-2) which has a charge of -1.

(5) Hydrogen always have a charge of +1 if it is bonded with a non-metal (as in the case of HCl) and always have a -1 charge if it is bonded with a metal (as in AlH3).

So for your problem, according to rule 2, the overall oxidation state of NO3 is -1.

NO3 = -1

According to rule 4, the O atom should have a -2 charge. But since the oxygen has a subscript in the formula, we need to multiply the charge by the subscript.

x + [(-2) (3)] = -1 where x is the oxidation state on N atom

solving for x,

x + (-6) = -1

x = -1 + (+6)

x = +5

Therefore, answer is N5+