The structures of beryllium chloride in the solid state and vapour phase, respectively, are:

• A

  chain and chain
• B

  dimeric and chain
• Correct answer
  C

  chain and dimeric
• D

  dimeric and dimeric

Solution

BeCl₂ exists as (BeCl₂)n polymeric chain in solid form, while BeCl₂ exists as dimer in vapour phase because $\mathrm{B}\mathrm{e}$ has vacant orbital and it is electron deficient.
In vapour state

In solid state

Hence, the correct answer is option: 'C'.