Final answer:
A molecule with three regions of electron density with one lone pair will have a bent or V-shaped molecular geometry because lone pairs occupy more space and repel the bonding pairs.
Step-by-step explanation:
A molecule with three regions of electron density where one is a lone pair will have a bent or V-shaped molecular geometry. According to the principles of VSEPR (Valence Shell Electron Pair Repulsion) theory, three regions of electron density would initially correspond to a trigonal planar electron-pair geometry were there no lone pairs involved. However, when one of these regions is a lone pair, the molecular geometry is altered. The lone pair occupies more space and repels the bonding electron pairs into a bent shape to minimize repulsion, leading to angles between the bonded atoms that are less than the ideal 120° of a trigonal planar arrangement.
This results in the noticeable bent configuration of the molecule. An example of such a molecular structure is water (H₂O), where the oxygen atom is the central atom with two hydrogen atoms bonded and two lone pairs of electrons, creating a bent molecular geometry.