Final answer:
The central atom with three lone pairs and two bonds has a trigonal bipyramidal electron pair geometry and a seesaw molecular structure, where the lone pairs occupy equatorial positions to minimize repulsions.
Step-by-step explanation:
When a central atom in a molecule has three lone pairs and two bonds, the resulting electron pair geometry and molecular structure must be determined based on the principles of VSEPR (Valence Shell Electron Pair Repulsion theory). The electron pair geometry describes the spatial arrangement of all pairs of electrons around the central atom, including bonding pairs and lone pairs, while the molecular structure describes the arrangement of the atoms in the molecule.
The central atom with three lone pairs and two bonds has a total of five regions of electron density, which corresponds to a trigonal bipyramidal electron pair geometry. According to VSEPR theory, lone pairs occupy more space than bonding pairs due to their greater repulsion. Thus, to minimize repulsions in a trigonal bipyramidal geometry, lone pairs should be placed in the equatorial positions rather than the axial positions. This leads to the molecular structure known as a seesaw, characterized by two bonds in an axial position and two lone pairs in equatorial positions with one lone pair remaining in the third equatorial position.