The number of valence electrons in an atom with the electronic configuration $1{\mathrm{s}}^2 2{\mathrm{s}}^2 2{\mathrm{p}}^6 3{\mathrm{s}}^2 3{\mathrm{p}}^3$ is

The total number of covalent bonds formed in the Lewis structures of given species respectively are:

(a) ${\mathrm{CO}}_3^{2-}$

(b) ${\mathrm{CCl}}_4$

(c) ${\mathrm{NF}}_3$

(d) ${\mathrm{HNO}}_3$

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?