In the compound Al2O3, aluminum has an oxidation number of 3, while oxygen's oxidation number is .

The oxidation number of Oxygen is -2.

if two electrons have the same n, the same ℓ, and the same ml, then they are in the same orbital. the pauli exclusion principle states that no two identical fermions (a fancy word for electrons and other subatomic particles like electrons) may occupy the same quantum state in an atom simultaneously.

c is the answer because when something is left after something evaporates that shows the chemical change.