Question

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

• A. chain and dimeric
• B. chain and chain
• C. dimeric and dimeric
• D. dimeric and chain

Answer 1

The Correct Option is A

Beryllium chloride (BeCl₂) exhibits different structures in the solid and vapor phases due to its ability to form different types of bonding under varying conditions.

1. Solid-state Structure of Beryllium Chloride:
   • In the solid state, beryllium chloride forms a polymeric chain structure.
   • Each beryllium atom is tetrahedrally coordinated, where it is bonded to two chloride ions covalently and has additional coordination with the chlorine atoms of neighboring units, resulting in a chain-like or polymeric structure.
   • This polymeric lattice structure helps in achieving stability through extended covalent bonding.
2. Vapor-phase Structure of Beryllium Chloride:
   • In the vapor phase, beryllium chloride predominantly exists as a dimer, Be₂Cl₄.
   • This dimeric structure arises because two BeCl₂ units share chloride ions, forming a stable four-membered ring.
   • The dimer formation helps in reducing the electron deficiency of the beryllium atoms by utilizing bridging chloride ions.

Therefore, the correct answer is that in the solid state, beryllium chloride forms a chain structure, and in the vapor phase, it exists as a dimeric structure.

Thus, the correct option is: chain and dimeric.