Final answer:
A molecule with 2 terminal atoms and 1 non-bonding pair of electrons on the central atom has a bent or V-shaped geometry, where the presence of the lone pair repels bonding electron pairs, altering the shape from a trigonal planar electron domain to a bent molecular geometry.
Step-by-step explanation:
A molecule with 2 terminal atoms and 1 non-bonding pair of electrons on the central atom would be expected to have bent or V-shaped geometry. This is because the lone pair of electrons occupies space and repels the bonding electron pairs, resulting in a molecular shape that is not linear. Considering a molecule like water (H2O) which has two bonding pairs and two lone pairs, we can see that its shape is bent due to the repulsion of the lone pairs. Although the standard angle in a tetrahedral geometry is approximated at 109.5 degrees, the bond angle in a molecule with two bonds and one lone pair tends to be less than that, ranging around 104.5 degrees as seen in water.
According to the VSEPR theory, the presence of a lone pair on the central atom leads to adjustments in the molecule's shape to minimize repulsions between electron pairs. When considering the regions of electron density (lone pairs and bonds), we can determine the electron domain geometry, which for a molecule with three regions of electron density is a trigonal planar; however, with one lone pair, the actual molecular shape is bent or V-shaped.