QJEEM23Chfd82: JEE Main 2023 Chemistry - Class 11 JEEM23Chfd82 Solution: Structures of in solid state, vapour phase and at very high…

$\mathrm{BeCl}_2$ forms a polymeric structure in the solid state due to coordination bonds formed by chlorine donating a lone pair of electrons to the beryllium atoms.

In the vapour phase at moderate temperatures, $\mathrm{BeCl}_2$ exists as a dimer, forming a bridge structure with two chlorine atoms connected to two beryllium atoms.

At very high temperatures, $\mathrm{BeCl}_2$ exists as monomers due to the high kinetic energy of the molecules, which overcomes the dimerisation tendency.