Why does sulfur have variable valency?

Answer 1

Oxygen is divalent, but sulphur exhibits variable valency of 2, 4 and 6 because of the presence of d -orbitals in sulphur. In sulphur, the excitation of np -electrons to nd -sub-shell gives rise to increase in number of unpaired electrons. Option D is correct.

Answer 2

Sulfur has variable valency because it can form different numbers of bonds with other elements. Sulfur can exhibit valencies of +2, +4, or +6 depending on the specific compound and bonding arrangements. This flexibility is due to sulfur's ability to expand its valence electron shell by using its d orbitals in addition to its s and p orbitals.