What is the decreasing order of $C - C$ bond length in the following compounds?
$[I]$ $C_2H_4$
$[II]$ $C_2H_2$
$[III]$ $C_6H_6$
$[IV]$ $C_2H_6$

When a chemical bond is formed,there is a decrease in

The compound in which the number of $d\pi - p\pi$ bonds are equal to those present in $ClO_4^{-}$ is:

Which of the following formulas does not correctly represent the bonding capacity of the atom involved?

Select the incorrect statement about $N_2F_4$ and $N_2H_4$ :
$(I)$ In $N_2F_4$,$d$-orbitals are contracted by electronegative fluorine atoms,but $d$-orbital contraction is not possible by $H$ atoms in $N_2H_4$.
$(II)$ The $N-N$ bond energy in $N_2F_4$ is more than the $N-N$ bond energy in $N_2H_4$.
$(III)$ The $N-N$ bond length in $N_2F_4$ is more than that in $N_2H_4$.
$(IV)$ The $N-N$ bond length in $N_2F_4$ is less than that in $N_2H_4$.
Choose the correct code:

Which one of the following is a correct set?