Find the total number of chemical species in which mentioned bond length decreases due to back bonding.
BF₃              (B–F) , B(OMe)₃      (B–O) ,        PF₃,       (P–F),
H₃SiNCO (N–Si) , B₃N₃H₆    (B–N) ,        NO₂^- (N–O),
O₃          (O–O)

Question

Find the total number of chemical species in which mentioned bond length decreases due to back bonding.

BF₃ (B–F) , B(OMe)₃ (B–O) , PF₃, (P–F),

H₃SiNCO (N–Si) , B₃N₃H₆ (B–N) , NO₂^- (N–O),

O₃ (O–O)

TestHub · Accepted Answer

BF₃ (B-F), B(OMe)₃ (B-O), and B₃N₃H₆ (B-N) undergo $2 p π - 2 p π$ back bonding from the lone pairs of F, O, and N into the vacant $2 p$ orbital of Boron.

H₃SiNCO (N-Si) undergoes $2 p π - 3 d π$ back bonding from the lone pair of Nitrogen into the vacant $3 d$ orbitals of Silicon.

PF₃ (P-F) exhibits $2 p π - 3 d π$ back bonding from the lone pairs of Fluorine into the vacant $3 d$ orbitals of Phosphorus.

This back bonding imparts partial double-bond character, decreasing the respective bond lengths in these five species, while O₃ and NO₂⁻ only show normal resonance.

Chemistry - CHEMICAL BONDING Question with Solution | TestHub

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