2022 O Level Chem P1 Q7 — Covalent Bonding Solution

Answer: D. Two counts are needed:

Total electrons in \(\text{CO}_2\): carbon has 6 electrons, oxygen has 8 each. Total = \(6 + 2 \times 8 = 22\) electrons.

Electrons used in C–O bonding: \(\text{CO}_2\) has two C=O double bonds. Each double bond is two shared pairs = 4 electrons. So bonding electrons = \(2 \times 4 = 8\).

22 total and 8 in bonding → row D.

A and B (16 total) are wrong: they undercount the electrons on each oxygen (probably forgetting the inner shell). C (4 bonding electrons) treats each double bond as one shared pair instead of two. Note that the lone pairs on each oxygen (4 per O) are not counted as bonding electrons — they sit on the O atom alone.