Question

Which molecule has a $$120$$ degree bond angle?

Answer 1

Hint: We need to know 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:
As we know, the bond angle of boron trichloride is equal to $${120}^{\circ }$$. Here, the boron is the central atom and three hydrogen atoms are linked with three chlorine atoms. But it does not contain any lone pair of electrons. Let’s see the structure of $$BC{l}_3$$

The structure of boron trichloride is equal to trigonal planar with $$s{p}^2$$ hybridization. The boron trichloride is a non – polar compound due to its symmetrical structure. The boron – chlorine bond is polar. Because, there is a difference between the electronegativity of boron and chlorine. Hence, all the B – Cl bonds lie at the bond angle $${120}^{\circ }$$. According to VSEPR theory, the molecular geometry of $$BC{l}_3$$ is equal to trigonal planar. And the bond angle of boron trifluoride is also $${120}^{\circ }$$. Here, the bromine is connected with three fluorine atoms.


Note:
We need to remember 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 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.