The Lewis structure of SO2 shows the arrangement of atoms and valence electrons in the molecule. Sulfur, the central atom, has six valence electrons, while each oxygen atom has six valence electrons.
The Lewis structure of sulfur dioxide (SO2) involves understanding the arrangement of atoms and valence electrons to represent the molecule’s bonding. A sulfur atom (S) and two oxygen atoms (O) make up the SO2 Lewis structure. The sulfur atom (S) is the center atom, and the two oxygen atoms (O) surround it at a bond angle of 119 degrees. The sulfur atom (S) and each oxygen atom (O) form two double bonds.
Here’s a detailed step-by-step guide:
- Count the Total Valence Electrons:
- Sulfur (S) is in Group 16 of the periodic table, so it has 6 valence electrons.
- Oxygen (O) is also in Group 16, and since there are two oxygen atoms, that’s 6×2=12 valence electrons.
- Total valence electrons = 6(fromS)+12(fromO)=18.
- Determine the Central Atom:
- Typically, the least electronegative atom is the central atom. Here, sulfur is less electronegative than oxygen, so sulfur will be the central atom.
- Place Electrons to Form Bonds:
- Place sulfur in the center and the two oxygen atoms on either side.
- Draw single bonds (one shared electron pair) between S and each O, which uses 4 electrons (2 for each bond).
- Distribute Remaining Electrons:
- You have used 4 electrons, so 18 – 4 = 14 electrons remain.
- Place these electrons around the oxygen atoms first to complete their octets (oxygen needs 8 electrons to achieve a stable configuration). Each oxygen now has 6 non-bonding electrons plus 2 from the bond with sulfur, totaling 8 electrons around each oxygen.
- After giving 6 electrons to each oxygen, 2 electrons are left. Place these on the sulfur atom.
- Check Formal Charges and Optimize:
- At this point, sulfur has only 6 electrons around it from bonds, which isn’t an octet. However, sulfur can expand its octet because it has d orbitals available.
- Convert one lone pair from one oxygen into another bond between sulfur and that oxygen. This gives sulfur an expanded octet with 10 electrons around it, but more importantly, it reduces formal charges:
- Resonance:
- SO2 actually exhibits resonance where the double bond can be with either oxygen, suggesting a hybrid structure where the sulfur-oxygen bonds are somewhere between single and double bonds.
Lewis Structure
The structure now has one double bond and one single bond with sulfur having an expanded octet. Here’s how it looks:
This structure explains the molecular shape of SO2, which is bent or V-shaped, due to the lone pair on sulfur causing electron-electron repulsion, leading to an O-S-O bond angle of approximately 119 degrees.