Question

what is the charge on an oxygen ion after it gains two electrons? -1 0 -2 +2

Explanation:

Step1: Recall electron charge

Electrons have a negative charge ($-1$ each).

Step2: Calculate charge after gain

Oxygen atom gains 2 electrons. Each electron is $-1$, so total charge change: $2\times(-1) = -2$. Original oxygen atom is neutral (charge 0), so new charge: $0 + (-2) = -2$.

Answer:

The option with -2 (the third option, labeled -2).