Question

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

Short answer

(a) Selenate, (b) Selenide, (c) Hydrogen selenide ion, (d) Hydrogen selenite ion.

Step-by-step solution

Analyze Ion (a)

The ion provided is \( \text{SeO}_4^{2-} \). This ion is analogous to the sulfate ion \( \text{SO}_4^{2-} \) and is part of a family of oxyanions where selenium acts similarly to sulfur. The name for this ion follows the pattern of 'sulfate' in this family but with selenium, so it is called **selenate**.

Analyze Ion (b)

The ion provided is \( \text{Se}^{2-} \). This is the simplest form of selenium ion, similar to the sulfide ion \( \text{S}^{2-} \). Following the naming convention, this ion is named **selenide**.

Analyze Ion (c)

The ion provided is \( \text{HSe}^{-} \). This is a hydrogen selenide ion. It is similar to the hydrogen sulfide ion \( \text{HS}^{-} \). The name for this ion follows the pattern with hydrogen added, thus it is called **hydrogen selenide ion**.

Analyze Ion (d)

The ion provided is \( \text{HSeO}_3^{-} \). This ion resembles the hydrogen sulfite ion \( \text{HSO}_3^{-} \). The ion is a derivative of the selenite \( \text{SeO}_3^{2-} \) with an additional hydrogen, so it is named as a **hydrogen selenite ion**.

Key concepts

Selenium Compounds

Selenium is a fascinating element that shares many similarities with sulfur, which makes the study of its compounds quite interesting. In chemistry, elements that display similar behavior often form analogous compounds. Selenium generally forms two kinds of compounds: selenides and selenates, among others. These compounds often mirror those of sulfur due to its position in the same group of the periodic table.
For instance, selenium can form tetrahedral oxyanions like \((\text{SeO}_4^{2-})\) known as selenate, analogous to sulfate \((\text{SO}_4^{2-})\). It can also form simple anions \(\text{Se}^{2-}\), resembling sulfide \(\text{S}^{2-}\).
Understanding selenium compounds is essential because selenium is crucial in biological systems, albeit in trace amounts. Its role often encompasses catalytic and antioxidant functions, thereby preventing cellular damage in living organisms.

Ion Naming Conventions

Naming ions in chemistry involves specific rules and conventions that make it universal and systematic for scientists across the globe. For simple anions, the element's name is taken and the suffix '-ide' is used. For example, selenium becomes selenide \(\text{Se}^{2-}\), much like sulfur becomes sulfide \(\text{S}^{2-}\).
However, when dealing with oxyanions, things get a bit more complicated. Oxyanions are polyatomic ions containing oxygen; their names depend on the number of oxygen atoms present. For instance, a sulfate ion \(\text{SO}_4^{2-}\) has one more oxygen than its sulfite counterpart \(\text{SO}_3^{2-}\). Similarly, selenate and selenite relate through their oxygen content. These conventions help chemists understand the structure and oxidation state of the compounds simply by their names.

Oxyanions

Oxyanions play a pivotal role in inorganic chemistry, primarily because they form a crucial component of numerous chemical compounds. They are ions consisting of one or more oxygen atoms bound to another element, often a non-metal like sulfur or selenium.
For example, the ion \(\text{SeO}_4^{2-}\) is known as selenate, while \(\text{SeO}_3^{2-}\) is selenite. The naming often reflects the proportion of oxygen atoms 1 longer names with the '-ate' suffix usually indicate a greater number of oxygens compared to their '-ite' counterparts.
Understanding the structure of oxyanions helps in predicting their reactivity, stability, and the type of compounds they can form. These ions are essential for synthesizing various applications in materials science and environmental chemistry.

Sulfur Analogs

Sulfur analogs refer to compounds where selenium acts similarly to sulfur. This is because selenium and sulfur lie in the same group on the periodic table and exhibit similar chemical behaviors. For instance, both form diatomic molecules in their elemental states and create similar bonding patterns when forming compounds.
Hydrogen selenide and hydrogen sulfide are sulfur analogs. Both possess similar chemical formulas, \(\text{HSe}^-\) and \(\text{HS}^-\) respectively. Their similarities also extend to the oxidized states — the oxyanion selenate \(\text{SeO}_4^{2-}\) mirrors sulfate \(\text{SO}_4^{2-}\) just as selenide \(\text{Se}^{2-}\) reflects sulfide \(\text{S}^{2-}\).
Understanding these analogs not only facilitates learning about selenium and sulfur compounds but also clarifying how chemical properties evolve down a group in the periodic table. This concept is a cornerstone in studying periodic trends and reactivity patterns in chemistry.