Question

The correct increasing order of the bond length angle among $B{F}_3,P{F}_3\text{ and Cl}{\text{F}}_3$ follow the order
(A) $B{F}_3$ <$P{F}_3$ <$Cl{F}_3$
(B) $P{F}_3$<$B{F}_3$<$Cl{F}_3$
(C) $Cl{F}_3$<$P{F}_3$<$B{F}_3$
(D) All have equal bond angle

Answer 1

Hint: We have to choose the correct option for the increasing bond angle among the given options. Bond angle is the angle between the two bonds originating from a common atom. Bond angle is the concept inside the molecular geometry of the molecule.

Complete answer:
Lets understand what is meant by bond angle for the better understanding of the question. Bond angle is the angle between the two bonds which originates from the common atom. Molecular geometry is the three dimensional arrangement of atoms in a molecule. It includes the shape of the molecule, the bond length and the bond angle and any other geometric parameters. The geometry of $B{F}_3$ is a trigonal planar in which the fluorine atoms lie in the same plane and have a bond angle of around 120 degree. The bond angle in $P{F}_3$ is 109 degree because there are lone pairs at the top of the molecule and the shape of the molecule is trigonal pyramidal. And the bond angle in $Cl{F}_3$ is 90 degree due to the presence of lone pairs in the molecule and the shape of the molecule is T shaped.

Hence the correct answer is option (C).

Note: While solving this question we must remember the best bond angle is 109.5 degree and it is always called as an ideal bond angle. The reason behind it is that a perfect tetrahedral is formed at this angle. This angle is found in H-C-H and in this the hydrogen atoms repel each other equally which leads to the formation of this angle.