Chemistry - CHEMICAL BONDING Question with Solution | TestHub

N(CH₃)₃: Although Nitrogen has a lone pair, the Carbon atoms in the methyl groups belong to the second period and lack empty d-orbitals to accept it.

P(CH₃)₃: Similar to trimethylamine, Carbon lacks empty orbitals to accept the lone pair from Phosphorus.

BF₄⁻: Boron is $s{p}^3$ hybridized in this tetrahedral ion; all its valence orbitals are completely filled by the four B-F bonds, leaving no empty orbital for back bonding from Fluorine.

BO₃³⁻: This is the only exception in the list where back bonding is possible between the lone pairs of Oxygen and the empty p-orbital of the $s{p}^2$ hybridized Boron.