Question

Which of the following is electron-deficient ?

• A. $P{H}_3$
• B. $(C{H}_3{)}_2$
• C. $(Si{H}_3{)}_2$
• D. $(B{H}_3{)}_2$

Answer 1

Answer: (D)

Boron is an element of 13 group and contains three electrons in its valence shell. When its compound $B{H}_3$ dimerises, each boron atom carry only 6 electrons that is their octet is incomplete.
Hence, $(B{H}_3{)}_2$ is an electron deficient compound.
In all other given molecules octet of central atom is complete.