Question 17

[setty.nith3707]

why isnt it trigonal planar? how do you know where the electrons go?

[enachbe18198]

wondering the same thing here

[jellywing_2058]

Lone pairs need to be as far away as possible from each other. Therefore, by positioning themselves on the equatorial positions (forming the T-shape) keeps the lone pairs 120 degrees away from each other and 120, 90 and 90 degrees from each of the 3 Fluorines.

On the other hand, if the lone pairs were on the axial positions, they would form an angle of 180 degrees with each other which is very stable; however this would also make them only 90 degrees away from each of the Fluorines, which is much less stable than the T-shape.

[mohsinalam5969]

The chlorine atom has five electron-pairs in its outer shell; three of these are in Cl-F bonds, two are non-bonding ("lone") pairs. These keep as far apart as possible, minimizing repulsion between each of the negatively charged clouds, by adopting a trigonal bipyramidal arrangement.

The two lone pairs occupy equatorial positions at an angle of 120° to each other; this gives the lowest energy arrangement of the electron pairs in the molecule.

Because repulsions involving lone pairs are stronger than those involving bond pairs, the F-Cl-F angle is a little under 180° so the molecule has a slightly bent T-shape.