In which of the following compounds B—F bond length is shortest? — Chemical Bonding Chemistry Question

💡 Solution & Explanation

Step 1: Analyze the bonding and electronic configuration of Boron in each compound. Boron has a vacant 2p orbital in BF_3, which allows for back-bonding (pπ - pπ) from the filled 2p orbitals of the Fluorine atoms. Step 2: This pπ - pπ back-bonding introduces partial double-bond character to the B-F bonds in BF_3, thereby shortening them. In BF_4^-, BF_3 ← NH_3, and BF_3 ← N(CH_3)_3, Boron forms 4 bonds, using its vacant 2p orbital to accept a coordinate bond, leaving no vacant orbital for back-bonding. Step 3: Therefore, the B-F bond length is shortest in BF_3. Thus, the correct option is (c).