Choose the best Lewis structure for SO4
The correct answer and explanation is :
The best Lewis structure for the sulfate ion (SO₄²⁻) involves considering the bonding and electron distribution in a way that minimizes formal charges while satisfying the octet rule for each atom involved.
Step-by-Step Explanation:
- Count the Total Valence Electrons:
- Sulfur (S) is in Group 16, so it has 6 valence electrons.
- Oxygen (O) is also in Group 16, so each oxygen atom has 6 valence electrons.
- Since the sulfate ion (SO₄²⁻) carries a 2- charge, we add 2 more electrons to account for the negative charge. The total number of valence electrons is:
[
6 \, (\text{from S}) + 4 \times 6 \, (\text{from O}) + 2 \, (\text{from the 2- charge}) = 32 \, \text{electrons}.
]
- Arrange the Atoms:
- The sulfur atom is the central atom since it is less electronegative than oxygen.
- The four oxygen atoms will be arranged around the sulfur atom.
- Bonding and Electron Pairs:
- Initially, place a single bond (2 electrons) between sulfur and each oxygen atom.
- This uses up (4 \times 2 = 8) electrons, leaving us with (32 – 8 = 24) electrons to be placed as lone pairs on the oxygen atoms.
- Complete the Octet Rule for Oxygen:
- Each oxygen atom will need 6 more electrons (3 lone pairs) to complete its octet.
- After placing lone pairs on the oxygen atoms, the total number of electrons used is (4 \times 6 = 24) electrons on the oxygen atoms.
- Double Bonds:
- To minimize formal charges, the sulfur atom can form double bonds with two of the oxygen atoms. This reduces the number of lone pairs on those oxygens and helps fulfill the octet rule more effectively for sulfur.
- The final structure consists of two double bonds and two single bonds between sulfur and oxygen.
- Formal Charges:
- Sulfur in the center has no formal charge in this structure (it follows the octet rule with 8 electrons around it).
- The oxygens with single bonds carry a -1 formal charge, while the oxygens with double bonds have no formal charge.
Final Structure:
The final Lewis structure of SO₄²⁻ shows sulfur in the center with two double bonds and two single bonds to oxygen atoms. The oxygen atoms with single bonds each carry a negative charge, while the sulfur atom and oxygen atoms with double bonds are neutral.
This structure satisfies the octet rule for all atoms and minimizes formal charges, making it the best Lewis structure for the sulfate ion.