Question

What is the oxidation number of the element n in the compound n2o5? 1. 3 2. 6 3. 5 4. 2 5. −6 6. 4 7. −2 8. −3 9. −5 10. −4?

Answer 1

Answer is: oxidation number of nitrogen is +5 (3. 5).
Oxygen has greater electronegativity than nitrogen, so oxygen has negative oxidation number, in this compound -2, so oxidation number of nitrogen is +5:
2 · x + 5 · (-2) = 0.
2x = 10.
x = 10 ÷ 2.
x = 5; oxidation number of nitrogen.
The sum of the oxidation numbers in a neutral compound is zero.