What is the oxidation state of nitrogen in NO3^-?

What is the oxidation state of nitrogen in NO3^-?

• A. +3
• B. +5
• C. +6
• D. 0

Answer: (B)

When assigning oxidation states, electrons in bonds are assigned to the more electronegative atom. Oxygen is more electronegative than nitrogen, so each O contributes a oxidation number of -2. With three oxygens, the total from oxygen is -6. The overall charge of the nitrate ion is -1, so if we call nitrogen’s oxidation state x, then x + (-6) = -1. Solving gives x = +5. So nitrogen is in the +5 oxidation state. The other options don’t balance to the overall -1 charge: +3 would give -3 total, +6 would give 0, and 0 would give -6.

When assigning oxidation states, electrons in bonds are assigned to the more electronegative atom. Oxygen is more electronegative than nitrogen, so each O contributes a oxidation number of -2. With three oxygens, the total from oxygen is -6. The overall charge of the nitrate ion is -1, so if we call nitrogen’s oxidation state x, then x + (-6) = -1. Solving gives x = +5. So nitrogen is in the +5 oxidation state. The other options don’t balance to the overall -1 charge: +3 would give -3 total, +6 would give 0, and 0 would give -6.