Question

Why BF3 if more covalent than BI3 though l atom is larger than F atom?

Answer 1

Dear Student,

For the formation of covalent, the size of the atoms must be comparable. More comparable the size is, strong will be the overlapping and so stronger will be the covalent bond.
The size of I is bigger, so there is a size difference between the two elements inducing ionic character in the molecule and so covalent character decreases.