Question

What is the difference between electronic and molecular geometries?

Answer 1

Molecular geometries depend upon the types and number of electron pairs around the central atom, same goes with electronic geometries but in electronic geometries, lone pairs are considered as an electron pair.

Complete answer:
The most basic difference between electronic and molecular geometries is that in molecular geometries, if there is any lone pair around the central atom, it is not considered as an electron group. While in electronic geometries, lone pairs are also considered as electron groups and the name is given accordingly.
Electron and molecular geometries are such geometries through which we can define the shape of any molecule.
Let us say that an atom has three electron groups and one of them is a lone pair of electrons, the lone pair is considered as an electron group and in molecular geometries the lone pair will not be considered as an electron group.
The name of the arrangement of atoms given through electronic geometry would be trigonal planar as there are three electron groups. And the name of the same kind of arrangement given through molecular geometry would be bent, as the lone pair has not been considered in molecular geometry.
The shape that the electron groups make in molecular geometry will be the same as in electronic geometry, but only the lone pairs will be excluded.
Similar thing will happen if there are four electron groups in which there are two lone pairs. The electronic geometry will be called tetrahedral and that of the molecular geometry will be called as bent again as the two lone pairs are excluded in it.

Note:
The bond angle in molecular geometry will remain the same despite the exclusion of lone pairs in it. The name of the molecular geometry will be the same as that of electronic geometry if there are no lone pairs of electrons in the molecule. Even if single bond electron groups are converted into lone pairs, the name of the electronic geometry will remain the same, but the name of molecular geometry will differ.