Problem 68 - Chemistry The Central Science

Question

Selenium, an element required nutritionally in trace quantities, forms compounds analogous to sulfur. Name the following ions: (a) \(\operatorname{SeO}_{4}^{2-},(\mathbf{b}) \mathrm{Se}^{2-},(\mathbf{c}) \mathrm{HSe}^{-},(\mathbf{d}) \mathrm{HSeO}_{3}^{-}\)

Step-by-Step Solution

Answer

The names of the given ions are: (a) selenate, (b) selenide, (c) biselenide, and (d) biselenite.

Step 1: Determine the oxidation state of selenium in each ion

Before naming the ions, we need to figure out the oxidation state of selenium in each ion. (a) \(\operatorname{SeO}_{4}^{2-}\): Since the charge of each oxygen is -2, selenium has an oxidation state of +6. (b) \(\mathrm{Se}^{2-}\): The ion itself shows selenium has a -2 oxidation state. (c) \(\mathrm{HSe}^-\): Since each hydrogen has a +1 charge, selenium has an oxidation state of -1. (d) \(\mathrm{HSeO}_{3}^-\): Each oxygen has a charge of -2 and each hydrogen has a charge of +1. Therefore, selenium has an oxidation state of +4.

Step 2: Name the ions based on the analogous sulfur ions

Now that we know the oxidation states of selenium in each ion, we can compare them to the corresponding sulfur ions: (a) \(\operatorname{SeO}_{4}^{2-}\): Analogous to the sulfate ion \(\mathrm{SO}_{4}^{2-}\), this ion is called selenate. (b) \(\mathrm{Se}^{2-}\): Analogous to the sulfide ion \(\mathrm{S}^{2-}\), this ion is called selenide. (c) \(\mathrm{HSe}^-\): Analogous to the bisulfide ion \(\mathrm{HS}^-\), this ion is called biselenide. (d) \(\mathrm{HSeO}_{3}^-\): Analogous to the bisulfite ion \(\mathrm{HSO}_{3}^-\), this ion is called biselenite. Thus, the names of the given ions are: (a) selenate, (b) selenide, (c) biselenide, and (d) biselenite.

Key Concepts

Naming Ions

is used to name them. This process has parallels in naming selenium compounds, where the corresponding selenium ions are named by the oxidation state of selenium and the presence of other elements like oxygen or hydrogen.

Selenium Compounds

), respectively. These compounds are found in various environmental and biological systems, playing roles in electronics, glass manufacturing, and as dietary supplements, given selenium's essential trace element status for various organisms.

Analogous Sulfur Ions

). Understanding these analogies helps in predicting the properties, reactions, and nomenclature of selenium compounds in chemistry.