Chemistry - CHEMICAL BONDING Question with Solution | TestHub

Statement-1 is correct. ${\text{BF}}_3$ is indeed a weaker Lewis acid than ${\text{BCl}}_3$. Statement-2 is also correct and provides the correct explanation. Due to the smaller size and higher electronegativity of fluorine, the overlap between the filled $2p$ orbital of fluorine and the vacant $2p$ orbital of boron is more effective (stronger back bonding) in ${\text{BF}}_3$ than the overlap between the $3p$ orbital of chlorine and the $2p$ orbital of boron in ${\text{BCl}}_3$. This stronger back bonding in ${\text{BF}}_3$ reduces the electron deficiency on boron, making it a weaker Lewis acid.