Question

What is the difference between electronic and molecular geometries?

Answer 1

See Below

Explanation:

Electron Geometry is the shape the electrons take around the central atom. These electrons can be in either a chemical bond or in lone pairs.
- Linear
- Trigonal Planar
- Tetrahedral
- Trigonal Bipyramidal
- Octahedral

Molecular Geometry
This is the shape the actual connections between atoms take in a compound. The shape is dictated by the electron geometry, though. The electron geometry is the scaffold, and the connections between the atoms depend on this scaffold.

Ammonia has electron geometry that is tetrahedral (4 electron groups around central atom). It has a lone pair, though, and if you put this lone pair on top, then the connections between N-H (3 of them) make the NH3 compound look like a camera on a tripod - this is called "Trigonal Pyramidal" - and this is its molecular geometry.