Final answer:
The number of lone pairs in a molecule like sulfur dioxide (SO₂) can be determined using VSEPR theory, with SO₂ having one lone pair designated as AX₂E. In sulfur tetrafluoride (SF₄), which is designated as AX₄E, there is one lone pair out of five electron pairs, with the lone pair's placement affecting molecular stability and geometry.
Step-by-step explanation:
The number of lone pairs in a molecule can be predicted using VSEPR theory, which helps us understand the three-dimensional shape of a molecule. For example, in the sulfur dioxide (SO₂) molecule, we apply the AXE method of electron counting to determine that there are two bonding pairs and one lone pair
The molecule is thus designated as AX₂E, which means it has a total of three electron pairs: two bonding pairs (X) and one lone pair (E). Because lone pairs are not shared between nuclei and require more space near the central atom, they affect the geometry of the molecule, causing repulsion that can be represented as LP-BP > BP-BP. Considering the molecule sulfur tetrafluoride (SF₄), we designate it as AX₄E, which indicates a total of five electron pairs, with one of those pairs being a lone pair. Deciding where to place this lone pair in the molecule's structure (axial or equatorial positions) affects the molecule's stability and geometry due to electrostatic repulsion between electron pairs.