Chapter 18, Problem 52R

To determine

To calculate: the oxidation number of iron (Fe) in the compound ${\text{Fe}}_{\text{2}}{\text{S}}_{\text{3}}$.

Answer to Problem 52R

The oxidation number of iron (Fe) in ${\text{Fe}}_{\text{2}}{\text{S}}_{\text{3}}$ is +3.

Explanation of Solution

Introduction:

The oxidation number of an element corresponds to the number of electrons gained or lost by the last elements. It is generally equal to the group number.

  ${\text{Fe}}_{\text{2}}{\text{S}}_{\text{3}}$ contain iron and sulfur atoms. The atomic number of iron is 26 and sulfur is 16. The electronic configuration of iron is $\left[\text{Ar}\right]{\text{3d}}^{\text{6}}{\text{4s}}^{\text{2}}$ .

The electronic configuration of sulfur is $\left[\text{Ne}\right]{\text{3s}}^{\text{2}}{\text{3p}}^{\text{4}}$ .

Iron loses 3 electrons, 2 from 4s, and 1 from 3d sub shell in order to get half-filled d subshell. The stability of half-filled is greater.

Sulfur gains 2 electrons in order to complete its octet.

Therefore, the oxidation state of iron is +3 in ${\text{Fe}}_{\text{2}}{\text{S}}_{\text{3}}$ .

Conclusion:

Hence, the oxidation number of iron (Fe) in ${\text{Fe}}_{\text{2}}{\text{S}}_{\text{3}}$ is +3.