Difference in hybridization of axial and equatorial chlorine atoms.

Unequal sharing of electrons between phosphorus and axial vs. equatorial chlorine atoms.

Greater repulsion experienced by axial bond pairs due to 90° interactions with equatorial bond pairs.

The presence of d-orbitals in phosphorus preferentially influences axial bond lengths.

Belong to outermost shell

Belong to penultimate shell

Belong to outermost shell and sometimes penultimate shell

Belong to penultimate shell and sometimes to outermost shell

Double bond is shorter than a single bond.

Sigma bond is weaker than $π$-bond.

Double bond is stronger than a sigma bond.

Covalent bond is stronger than hydrogen bond.

One sigma $\left( {\rm{\sigma }} \right)$and one pi $\left( {\rm{\pi }} \right)$-bond

One sigma $\left( {\rm{\sigma }} \right)$and two pi $\left( {\rm{\pi }} \right)$-bonds

One sigma $\left( {\rm{\sigma }} \right)$ and one and a half pi $\left( {\rm{\pi }} \right)$-bond

One sigma $\left( {\rm{\sigma }} \right)$ bond

$s - s$ orbitals

$p - p$ orbitals

$s - p$ orbitals

$s - p - s$ orbitals

Energy is absorbed

Forces of attraction overcome forces of repulsion

Forces of repulsion overcome forces of attraction

Forces of attraction are equal to forces of repulsion

${\rm{NO}}_3^ -$

${\rm{SO}}_3^{2 - }$

${\rm{BO}}_3^{3 - }$

${\rm{CO}}_3^{2 - }$

${\rm{H}}$

${\rm{Be}}$

${\rm{B}}$

${\rm{N}}$

$17$

$16$

$15$

$6$

${\rm{C}}{{\rm{l}}_2}{{\rm{O}}_6}$

${\rm{C}}{{\rm{l}}_2}{{\rm{O}}_7}$

${\rm{C}}{{\rm{l}}_2}{\rm{O}}$

${\rm{Cl}}{{\rm{O}}_2}$

$2,{\rm{ }}5$

$3,{\rm{ }}4$

$4,{\rm{ }}3$

$5,{\rm{ }}2$