Question 8
How many electrons does a hydrogen atom end up with in its shell once it has formed a covalent bond?
The right answer is the one marked above.
Two. Hydrogen has only the first shell, which is full at two electrons — the helium arrangement. One shared pair is enough.
Eight applies to every other atom in these molecules, but hydrogen has no room for eight. One is the count before bonding. Four would need two bonds, and hydrogen never forms more than one.