Question

The correct increasing order of bond angle is:
A.$P{F_3} \approx N{F_3} < B{F_3} < {I_3}^ -$
B.$P{F_3} < N{F_3} < B{F_3} < {I_3}^ -$
C.${I_3}^ - < B{F_3} \approx N{F_3} < P{F_3}$
D.$B{F_3} < N{F_3} \approx P{F_3} < {I_3}^ -$

Answer 1

We need to remember that the bond angle is the angle present between two bonds which is occupied in a covalent species. Hence, there should be at least two bonds in that covalent species. The lone pair repulsion mainly affects the bond angle. Therefore, if the central atom contains the lone pair of electrons, the angle of the compound will decrease.

Complete answer:
The bond angle phosphorus trifluoride and boron trifluoride are not equal. Hence, option (A) is incorrect.
The correct increasing order of bond angle is $P{F_3} < N{F_3} < B{F_3} < {I_3}^ -$. Among these options, the bond angle of $P{F_3}$ is smaller than $B{F_3}$ and $N{F_3}$ which is equal to ${97^o}$. Because, here, F acts as lone pair donor and a vacant d orbital is present in phosphorus. And it causes a decrease in the bond angle and bond length due to less repulsion. But in the case of $N{F_3}$ it does not have a vacant d- orbital. so the bond angle is greater than $P{F_3}$.
And the bond angle of $B{F_3}$ is greater than$N{F_3}$. Because, the boron has three valence electrons and it is shared with fluorine atoms. And it also has $s{p^2}$ hybrid orbitals. But in the case of $N{F_3}$, nitrogen has five valence electrons. And only three N is used to share with the F atom. The remains two F atom act as lone pair. Therefore, the bond angle of $N{F_3}$(${101.9^o}$)is less than $B{F_3}$(${120^o}$).
And ${I_3}^ -$ion has a higher bond angle. Because it is linear in shape. Therefore, the bond angle is ${180^o}$. Hence, option (B) is correct.
The increasing order of bond angle is not equal to ${I_3}^ - < B{F_3} \approx N{F_3} < P{F_3}$. Because, among the given compounds,${I_3}^ -$ ion has the highest bond angle. Hence, option (C) is incorrect.
The bond angle of $P{F_3}$ is not equal to$N{F_3}$. Hence, the option (D) is incorrect.

Hence, option (B) is correct.

Note:
We must have to know that the bond angle mainly depends on the shape and hybridization of a compound. If the compounds have the same hybridization, then the sum of the lone pair and bond pair is equal to the same. Hence, the bond angle becomes equal. And the electronegativity and shape of molecules also affect the bond angle. The bond angle decreases with decreasing electronegativity.