SF6 is used in high voltage generators and switch gears. Why?

Explanation

Structures of `NH_3^+` and `NH_3` are as given below:

In `NH_4^+` all the four electron pairs around N-atom are bond pairs. Thus H-N-H angle in `NH_4` is expected to be `109^@28.`. In `NH_3`, there are three bond pairs and one lone pair. As lone pair-bond pair repulsion is more than bond pair-bond pair repulsion, H-N-Hangle is less than `109^@ 28.`.