Question

The central atom's number of valence electrons in __________ makes it an exception to the octet rule. nh3 sef2 bf3 asf3 cf4

Answer 1

Answer:

$\boxed{\text{BF}_{3}}$

Explanation:

You must draw the Lewis structure for each molecule, trying to give every atom an octet.

In the structures below, every molecule except one has a central atom with octet. That molecule is  

$\boxed{\textbf{BF}_{3}}$

The B atom has only six electrons in its valence shell, so it violates the octet rule.