In which of the following compounds is the octet rule not followed?

Compound $X$ is the anhydride of sulphuric acid. The number of $\sigma$-bonds and the number of $\pi$-bonds present in $X$ are,respectively:

Which of the following does not obey the octet rule?

The $B-F$ bond dissociation energy in $BF_3$ is $646 \, kJ \, mol^{-1}$,whereas the $C-F$ bond dissociation energy in $CF_4$ is $515 \, kJ \, mol^{-1}$. Which of the following is the correct reason for the $B-F$ bond dissociation energy being higher than the $C-F$ bond dissociation energy?

Identify the type of bonding in $CCl_4$ and $CaH_2$.

The correct order of increasing $C-O$ bond strength of $CO, CO_3^{2-}, CO_2$ is