NTA Abhyas JEE Main2020Chemistryp Block Elements (Group 13 & 14)Practice
A l C l 3 forms dimer in vapour phase but B C l 3 does not because
Options
- AIn A l there are vacant d orbitals in which it accommodates lone pair from chlorine atoms
- BIn B C l 3 there is back bonding
- CThere is hydrogen bonding in between two A l C l 3 molecules in vapour phase
- DNone of the above
Correct answer
A. In A l there are vacant d orbitals in which it accommodates lone pair from chlorine atoms
Step-by-step solution
The formation of stronger backbond ( 3 p → 2 p overlap in B C l 3 and weaker 3 p → 3 p overlap in A l C l 3 ) reduces the electron deficiency of the central atom and thus dimerisation tendency is reduced. So A l C l 3 can form a dimer but B F 3 and B C l 3 cannot.