Chapter 7, Problem 107A

Interpretation Introduction

Interpretation:

The oxyanions sulfate and sulfite needs to be compared.

Concept introduction:

In an oxyanion, the non metal is bonded with one or more oxygen atoms. This is also known as polyatomic ion. Depending on the number of oxygen atom, the oxidation state of the central non-metal is determined. The suffix used in the name of the polyatomic ion depends on the oxidation state.

Answer to Problem 107A

When sulfur covalently bonds with three oxygen atoms then it called sulfite. The formula is ${\text{SO}}_{\text{3}}{}^{2-}$.

And when sulfur covalently bonds with four oxygen atoms then it called sulfate. Its formula is ${\text{SO}}_4{}^{2-}$.

Explanation of Solution

Electron configuration of sulfur is as follows:

${\text{S=1s}}^{\text{2}}{\text{2s}}^{\text{2}}{\text{2p}}^{\text{6}}{\text{3s}}^{\text{2}}{\text{3p}}^{\text{4}}$

Sulfur can exists in the +4 by losing its four $\text{3p}$ electrons and +6 oxidation state by losing two $\text{3s}$ electrons and four $\text{3p}$ electrons. Oxygen is an electron-loving non-metal in group 16. It takes two electrons to form a pseudo-noble electronic configuration. When sulfur form +6 oxidation state, it has two vacant $\text{3s}$ orbital and three vacant $\text{3p}$ orbital available for bonding with four oxygen atoms. When sulfur is in +4 oxidation state it has only it’s vacant $\text{3p}$ orbitals to bond with three oxygen atoms.

Conclusion

Thus, when sulfur covalently bonds with three oxygen atoms then it called sulfite. The formula is ${\text{SO}}_{\text{3}}{}^{2-}$.

And when sulfur covalently bonds with four oxygen atoms then it called sulfate. Its formula is ${\text{SO}}_4{}^{2-}$.