Formal charge on sulfur in the lewis structure of so3 in which all atoms have an octet configuration?
The Correct answer and Explanation is:
To determine the formal charge on sulfur in the Lewis structure of sulfur trioxide (SO₃), we first need to draw the correct Lewis structure while ensuring all atoms satisfy the octet rule.
Lewis Structure of SO₃
- Valence Electrons Calculation:
- Sulfur (S) has 6 valence electrons.
- Each oxygen (O) has 6 valence electrons, and there are three oxygen atoms.
- Total valence electrons = 6 (from S) + 3 × 6 (from O) = 24 electrons.
- Initial Structure:
- Place sulfur at the center, as it is the least electronegative atom.
- Connect sulfur to three oxygen atoms with single bonds. This uses 6 electrons (2 electrons per bond).
- Completing the Octets:
- After forming single bonds, we have 18 electrons remaining (24 – 6 = 18).
- Distribute these remaining electrons to the oxygen atoms to satisfy their octets. Each oxygen needs 6 more electrons (2 lone pairs) to complete their octet.
- This distribution gives three lone pairs on each oxygen, consuming all 18 electrons.
- Adjusting for Octet Rule:
- To minimize formal charges, we can convert some lone pairs from oxygen into double bonds with sulfur. Thus, each oxygen forms a double bond with sulfur. The final structure shows sulfur in the center bonded to three oxygen atoms via double bonds.
Formal Charge Calculation
The formula for calculating the formal charge (FC) of an atom is:
[
\text{FC} = \text{Valence electrons} – \text{Non-bonding electrons} – \frac{1}{2} \times \text{Bonding electrons}
]
For sulfur in SO₃:
- Valence Electrons (S): 6
- Non-bonding Electrons: 0 (as all electrons are involved in bonds)
- Bonding Electrons: 6 (2 electrons from each of the three S=O double bonds)
Using the formula:
[
\text{FC (S)} = 6 – 0 – \frac{1}{2} \times 6 = 6 – 0 – 3 = +3
]
Conclusion
In the Lewis structure of SO₃, sulfur has a formal charge of +0 when represented correctly with three double bonds to oxygen, and all atoms follow the octet rule. Each oxygen atom has a formal charge of 0, making the entire molecule neutral. Thus, the stable resonance structures and their corresponding formal charges indicate the correct Lewis representation of sulfur trioxide.