Question

an atom of oxygen has six electrons in its outermost ring and requires two more to become stable. what is the valence number of oxygen?
+8
-2
+2
-8

Explanation:

Step1: Define valence number logic

Valence number reflects electrons gained/lost for stability.

Step2: Analyze oxygen's electron need

Oxygen gains 2 electrons, so charge = $0 + (-2) = -2$

Answer:

-2