Final answer:
For a central atom with five electron domains, the electron-domain geometry is trigonal bipyramidal, but molecular geometry can vary depending on lone pairs. Six electron domains result in octahedral electron-domain geometry, with potential variations in molecular geometry due to lone pairs.
Step-by-step explanation:
Understanding the electron-domain geometry is essential for predicting the molecular geometry of a molecule. For a central atom surrounded by five electron domains (bonding and lone pairs), the electron-domain geometry is trigonal bipyramidal.
If there are no lone pairs, the molecular geometry remains the same as the electron-domain geometry; however, with lone pairs, the molecular shape could be seesaw, T-shaped, or linear depending on the number of lone pairs.
Similarly, for a central atom with six electron domains, the electron-domain geometry is octahedral. With no lone pairs, the molecular geometry matches the electron-domain geometry. When lone pairs are present, the molecular geometry can alter to square pyramidal or square planar, depending on the disposition of the lone pairs.
The arrangement of these domains is optimized to minimize repulsions, resulting in the lowest energy and most stable configuration for the molecule.