Which compound is electron deficient?
- PCl3
- BCl3
- CCl4
- PCl5
Answer
(2) BCl3
Solution
In BCl3, boron (3 valence electrons) forms three B–Cl bonds, so it has only 6 electrons in its valence shell (incomplete octet).
∵ As per NCERT, the trihalides of boron are electron-deficient molecules and act as Lewis acids, e.g. BCl3 + :NH3 Cl3B NH3.
In CCl4 carbon has a complete octet, and in PCl5 phosphorus has 10 electrons (expanded octet). In PCl3 phosphorus has a complete octet (three bond pairs and one lone pair).
∴ BCl3 is the electron-deficient compound.
Answer: (2)