Question

Which of the elements below is most likely to form compounds in which it has an incomplete octet?

• A. $B$
• B. $C$
• C. $N$
• D. $O$
• E. $F$

Answer 1

Answer: (A)

$B$

Option A is the correct answer.

Boron forms compound in an incomplete octet state. An image might help to understand better.

For example, in $B{F}_3$, Boron has $3$ valence electrons and each of the three $F$ atoms has $7$ valence electrons each. Thus, Boron and Fluorine mutually share their electrons to fulfill their octet.

Three single covalent bonds are formed where Boron shares it's $3$ valence electrons with three Fluorine atoms so that each Fluorine atom now has $8$ electrons in its outermost orbit. But, although the Fluorines share their $1$ valence electron each with Boron, Boron's octet is not fulfilled. It now has ($3+3$) that is $6$ electrons. The octet is not yet fulfilled.