Question

In which of the following compounds does the central atom violate the octet rule?
$(\text{Given: Atomic number},Se=34,As=33,B=5,N=7)$

• A. $N{H}_3$
• B. $Se{F}_2$
• C. $B{F}_3$
• D. $As{F}_3$

Answer 1

The correct option is C $B{F}_3$

The lewis dot structure of given molecules are as follow:

The central atoms $N,Se$ and $As$ in $N{H}_3,Se{F}_2$ and $As{F}_3$ respectively have 8 valence electrons. But in the case of $B{F}_3$, boron has an incomplete octet of only 6 electrons in its valence shell and hence violates the octet rule.