What are important question in number system and polynomials class 9.

state of any element:

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

For example, the

H

2

O

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

N

O

-1

3

ion is -1).

(3) All elements from Group 1A has an oxidation state of +1 (e.g.

N

a

+1

,

L

i

+1

). All Group 2A and 3A elements have an oxidation state of +2 and +3, respectively. (e.g.

C

a

2+

,

M

g

2+

,

A

l

3+

)

(4) Oxygen always have a charge -2 except for peroxide ion (

O

2-

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

H

C

l

) and always have a -1 charge if it is bonded with a metal (as in

A

l

H

3

).

So for your problem, according to rule 2, the overall oxidation state of

N

O

−

3

is -1.

N

O

−

3

= -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

N

5+