Which of the following molecule has weakest (p\pi - d\pi) back bonding ? — Chemical Bonding Chemistry Question

💡 Solution & Explanation

Step 1: Examine the bonding in each of the polyatomic species. A coordinate (dative) bond is formed when one atom provides both electrons of the shared pair. Step 2: In H_3O^+, oxygen donates a lone pair to H^+ to form a coordinate bond. In BF_4^-, a fluoride ion (F^-) donates a lone pair to the vacant orbital of BF_3 to form a coordinate bond. In NH_4^+, nitrogen donates a lone pair to H^+ to form a coordinate bond. In HF_2^-, the species exists as a hydrogen-bonded adduct [F—H...F]^- held by strong electrostatic hydrogen bonding, not a coordinate covalent bond. Step 3: Therefore, HF_2^- does not contain any coordinate covalent bond. Thus, the correct option is (c).