Special note for PCl5:
In PCI₃, there are two types of bonds-Two (P-Cl) axial bond and three (P-CI) equatorial bonds.
Due to repulsion between Cl atom: (P-Cl) axial bonds are longer in bond length (240 pm) and are weaker while (P-Cl) equatorial bonds are shorter in bond length (202 pm). So, PCl5 on heating gives
PCI,5 --- PCl3 + Cl2
