In which of the following molecules, the central atom expands its covalency by excitation but not its octet?

(a) ${\mathrm{ICl}}_2^{-}$

(b) ${\mathrm{C}}_2{\mathrm{H}}_4$

(c) ${\mathrm{BF}}_4^{-}$

(d) ${\mathrm{SO}}_2$

Maximum number of lone pairs is present in Lewis dot structure of which compound?

The ratio of $\sigma$ to $\mathrm{\pi }$ bonds in naphthalene is

What is true about $\mathrm{CO}$ molecule?

$\mathrm{a}.$ It has two lone pairs.

$\mathrm{b}.$ It has one dative bond.

$\mathrm{c}.$ It has two $\mathrm{\pi }$ bonds.

$\mathrm{d}.$ It has one $\mathrm{\sigma }$ bond.