Question

In which of the following molecule back bonding is present?

• A. $B{F}_3$
• B. $H_{2}O$
• C. $N{H}_3$
• D. $HF$

Answer 1

Answer: (A)

$B{F}_3$

BF3 has trigonal planar structure all the three BF bonds lie in the plane and thus p-orbitals of boron and fluorine become parallel

Boron has empty p-orbital and p-orbital of fluorine contains lone pair and hence Boron act as Lewis acid and fluorine as Lewis base. Fluorine donates it's a lone pair to Boron and this bonding is called back bonding

So, the correct answer is 'BF3'.