WAEC Chemistry 2018 Paper

Concept:Count the shared electrons in the covalent bonds of the displayed Lewis structure.Explanation:The structure contains four $\mathrm{C-H}$ single bonds and one $\mathrm{C=C}$ double bond.Each $\mathrm{C-H}$ single bond has one shared pair, which is 2 shared electrons.So, the four $\mathrm{C-H}$ bonds contribute $4 \times 2 = 8$ shared electrons.A double bond has two shared pairs, which is $2 \times 2 = 4$ shared electrons.Total shared electrons in the compound: $8 + 4 = 12$.Answer:D. 12