Video Transcript
Which of the following abbreviations represents an SO2 molecule according to the VSEPR theory? The atomic number of sulfur is 16, and the atomic number of oxygen is eight. (A) AX2, (B) AX2E, (C) AXE2, or (D) AX2E2.
We can use the Lewis structure diagram for SO2, or sulfur dioxide, to answer this question. Using this diagram, we can determine which AXE configuration is correct for sulfur dioxide. When using the AXE method, the A-term represents the central atom. In this case, the sulfur atom is our central atom. The X-term represents the bonding domains, which is a site on the central atom where bonding is occurring with another atom. The 𝑚-term is a whole number representing the number of bonding domains.
We can begin applying the AXE method to our sulfur dioxide molecule, where A represents our sulfur atom and X represents the bonding domains on the sulfur atom. This structure contains two bonding domains. It is worth noting that even though one of the oxygen atoms is engaging in a double bond with sulfur, this is still just one bonding domain, as it is still only one site where bonding is occurring between two atoms.
The final term E represents the lone pairs, with 𝑛 being a whole number representing the number of lone pairs on the central atom. A lone pair is a pair of valence electrons that are not shared in a covalent bond. Lone pairs are represented by two dots in our diagram. When using the AXE method, we only count the lone pairs present on the central atom. There is one lone pair on our central sulfur atom. Note that it is not necessary to write a subscript of one as it is implied.
Therefore, the answer choice that matches the AXE abbreviation we have determined for sulfur dioxide is answer choice (B), AX2E.
