Chemistry - CHEMICAL BONDING Question with Solution | TestHub

A molecule is said to be electron deficient because there are not enough valence electrons to form the expected number of covalent bonds. For example, in ${\mathrm{B}}_2{\mathrm{H}}_6$, there are only 12 electrons, three from each boron atoms and six from hydrogen, while ethane possesses 14 such electrons.

Also in ${\mathrm{BCl}}_3$, B has six electrons in its outermost orbit. So, the number of electron deficient molecules are 2.