Write the resonance structures of SO3 and NO2
The Correct Answer and Explanation is:
The resonance structures of SO₃ (sulfur trioxide) and NO₂ (nitrogen dioxide) are depicted below, and I’ll explain their reasoning.
SO₃ (Sulfur Trioxide) Resonance Structures
SO₃ is a molecule with sulfur as the central atom and three oxygen atoms surrounding it. It has a trigonal planar structure with an sp² hybridization at the sulfur atom. The molecule is symmetrical, and the sulfur atom is double-bonded to each oxygen atom.
Resonance Structures of SO₃:
- The first resonance structure shows sulfur with double bonds to all three oxygen atoms. This gives sulfur an oxidation state of +6.
- The second resonance structure shows the double bonds being shifted around, so that one of the oxygen atoms is now single-bonded with sulfur, and a negative formal charge is placed on that oxygen. The other oxygen atoms have a formal positive charge on sulfur.
- The third resonance structure involves a similar shifting of bonds, where the second oxygen atom is now single-bonded to sulfur.
These resonance structures demonstrate that the bonding in SO₃ is delocalized over all three oxygen atoms, and the molecule does not have fixed single or double bonds. Instead, the bonds are equivalent and shared.
NO₂ (Nitrogen Dioxide) Resonance Structures
NO₂ is a molecule with nitrogen as the central atom and two oxygen atoms attached. The nitrogen atom in NO₂ is sp² hybridized, and there is an odd number of electrons in the molecule, making it a free radical.
Resonance Structures of NO₂:
- The first resonance structure shows a nitrogen-oxygen double bond and a nitrogen-oxygen single bond, with the single-bonded oxygen carrying a negative formal charge and nitrogen carrying a positive formal charge.
- The second resonance structure shows the double bond between nitrogen and oxygen shifted to the other oxygen, with the formal charges on the nitrogen and oxygen atoms switched.
In NO₂, the resonance structures help to explain the presence of an unpaired electron (radical) on one of the oxygen atoms, as well as the delocalization of charge in the molecule. The resonance also accounts for the overall bond order being between a single and a double bond.
Summary
- SO₃ has three equivalent resonance structures involving delocalized electrons over all three oxygens.
- NO₂ has two resonance structures, with a radical electron on one of the oxygen atoms and formal charge delocalization between nitrogen and oxygen.
