Question

Which one of the following is least covalent in nature ?

• A. $N{F}_3$
• B. $Bi{F}_3$
• C. $P{F}_3$
• D. $Sb{F}_3$

Answer 1

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

The covalent character in case of same anionic species, depends upon the size of cation and decreases with increase in the size of central atom.

Small size of cation, large size of anion, and high charge on both species results in greater covalent character. But Bi (cation) have large size as the down the group atomic size increase.

All trihalides are covalent except $Bi{F}_3$ which is ionic.

Option B is correct.