Question

which of the following has the lowest number of unshared electrons around the central atom? xef4 so2 cif3 h2o sf6

Explanation:

Unshared electrons (lone pairs) around central atoms are calculated via valence electrons and bonding:

• $\text{XeF}_4$: Xe has 8 valence e⁻; 4 bonds to F use 8 e⁻ → 2 lone pairs (4 unshared e⁻).
• $\text{SO}_2$: S has 6 valence e⁻; 2 double bonds to O use 8 e⁻? No—2 bonds (each 2 e⁻) + 1 lone pair → 2 unshared e⁻.
• $\text{ClF}_3$: Cl has 7 valence e⁻; 3 bonds to F use 6 e⁻ → 2 lone pairs (4 unshared e⁻).
• $\text{H}_2\text{O}$: O has 6 valence e⁻; 2 bonds to H use 4 e⁻ → 2 lone pairs (4 unshared e⁻).
• $\text{SF}_6$: S has 6 valence e⁻; 6 bonds to F use all 12 e⁻ (expanded octet) → 0 lone pairs (0 unshared e⁻).

$\text{SF}_6$ has the lowest number of unshared electrons.

Answer:

SF₆