BF_(3)existsas discretemoleculesbut BH_(3) existsas dimer. Explain .

1.	BF_(3)existsas discretemoleculesbut BH_(3) existsas dimer. Explain .
Answer» Solution :Due to `ppi-ppi` backbonding, the LONE pairof electronsof F is donatedto the B-atom. This delocalization reducesthe deficiency ofelectrons on Bthereby INCREASING the stability of `BF_(3)` MOLECULE. Due to absenceof lone pair of electrons on H-atom, this compensationdoes not occurin `BH_(3)`. In otherwords, electron deficiency of B stays and HENCE to reduce its electron deficiency, `BBH_(3)` dimerises to form `B_(2)H_(6)`.

Discussion