Question

Describe the bonding in \(\mathrm{SO}_{2}\) and \(\mathrm{SO}_{3}\) using the localized electron model (hybrid orbital theory). How would the molecular orbital model describe the \(\pi\) bonding in these two compounds?

Short answer

In both SO₂ and SO₃, sulfur undergoes sp² hybridization, forming 3 equivalent sp² hybrid orbitals. In SO₂, sulfur forms two σ bonds with two oxygen atoms and has one lone pair of electrons in its third sp² orbital. In SO₃, sulfur forms three σ bonds with three oxygen atoms. The π bonding in both compounds occurs through the sideways overlap of the unhybridized 2p orbitals of sulfur and oxygen atoms. In SO₂, there is one π bond, while in SO₃, three π bonds are distributed over all three sulfur-oxygen bonds due to resonance structures. The localized electron model describes the σ bonding, while the molecular orbital model explains the π bonding in both compounds.

Step-by-step solution

Identify the type of hybridization in SO₂ and SO₃ compounds

First, we need to determine the hybridization of sulfur atoms in both compounds, SO₂ and SO₃. For SO₂: Sulfur has 6 valence electrons and in SO₂, it is double bonded to one oxygen and single bonded to another oxygen atom. Therefore, sulfur uses 3 of its valence electrons to form bonds with oxygen atoms. To accommodate these 3 electron domains (double bond, single bond, and lone pair), sulfur must undergo sp² hybridization. For SO₃: Sulfur has 6 valence electrons and in SO₃, it is double bonded to each of the 3 oxygen atoms. This means, sulfur uses all its valence electrons to form bonds with the oxygen atoms. To accommodate these 3 electron domains (all double bonds), sulfur must undergo sp² hybridization as well.

Describe the σ bonding in SO₂ and SO₃ using hybrid orbital theory

For SO₂: In SO₂, sulfur undergoes sp² hybridization and forms 3 equivalent sp² hybrid orbitals. One of the sp² hybrid orbitals forms a σ bond with one oxygen atom's 2p orbital, and another sp² hybrid orbital forms a σ bond with the other oxygen atom's 2p orbital. The third sp² hybrid orbital of sulfur contains a lone pair of electrons. For SO₃: In SO₃, sulfur undergoes sp² hybridization and forms 3 equivalent sp² hybrid orbitals. Each sp² hybrid orbital forms a σ bond with one oxygen atom's 2p orbital. There are three σ bonds in total between sulfur and oxygen atoms in the SO₃ compound.

Describe the π bonding in SO₂ and SO₃ using molecular orbital theory

For SO₂: In SO₂, apart from the σ bonds as mentioned previously, sulfur and oxygen atoms also form π bonds. The double bond between sulfur and oxygen atom consists of one σ bond and one π bond. The π bond is formed through the sideways overlap between unhybridized 2p orbitals of sulfur and oxygen atoms. For SO₃: In SO₃, each sulfur-oxygen double bond consists of one σ bond and one π bond. The π bond is formed through the sideways overlap between the unhybridized 2p orbitals of sulfur and oxygen atoms. There are three π bonds in total in the SO₃ compound, and each π bond is distributed over all three sulfur-oxygen double bonds due to the resonance structures in SO₃.

Compare the π bonding in SO₂ and SO₃

In both SO₂ and SO₃, the π bonds are formed between the unhybridized 2p orbitals of sulfur and oxygen atoms through the sideways overlap. In SO₂, there is one π bond between the sulfur and one oxygen atom, whereas in SO₃, there are three π bonds distributed over all three sulfur-oxygen bonds due to resonance structures. In conclusion, the localized electron model (hybrid orbital theory) helps us describe the σ bonding in SO₂ and SO₃ compounds, while the molecular orbital model explains the π bonding nature in both compounds.