* Oxygen's usual oxidation number: Oxygen typically has an oxidation number of -2, unless it's in a peroxide (like H₂O₂) or a superoxide.

* The overall charge of NO₂: NO₂ is a neutral molecule, meaning its overall charge is 0.

Let's set up an equation:

* Let x be the oxidation number of N.

* We have two oxygen atoms, each with an oxidation number of -2.

* The sum of the oxidation numbers must equal the overall charge of the molecule (0).

Equation: x + 2(-2) = 0

Solving for x:

* x - 4 = 0

* x = +4

Therefore, the oxidation number of N in NO₂ is +4.