Question

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

Short answer

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

Step-by-step solution

Identify the Base Element

Selenium (Se) forms compounds similar to sulfur (S) because they belong to the same group of the periodic table. This characteristic helps in naming the ions similar to those of sulfur-based compounds.

Naming the Tetraoxoanion

For ion (a) \[ \mathrm{SeO}_{4}^{2-} \]Analogous to sulfate (\(\mathrm{SO}_4^{2-}\)), this ion is named selenate.

Naming the Simple Anion

For ion (b) \[ \mathrm{Se}^{2-} \]Analogous to the sulfide ion (\(\mathrm{S}^{2-}\)), this ion is named selenide.

Naming the Hydrogen Anion

For ion (c) \[ \mathrm{HSe}^{-} \]Analogous to the hydrogen sulfide ion (HS\(^{-}\)), this ion is named hydrogen selenide ion.

Naming the Hydrogen Oxoanion

For ion (d) \[ \mathrm{HSeO}_{3}^{-} \]Analogous to the hydrogen sulfite ion (H\(\mathrm{SO}_3^{-}\)), this ion is named hydrogen selenite ion.

Key concepts

Selenium Compounds

Selenium is a fascinating element that plays a crucial role in both chemistry and biology. It's essential for the proper functioning of many organisms, including humans, although only in very small amounts. Selenium compounds are often similar in structure and properties to sulfur compounds. This is because selenium and sulfur belong to the same group in the periodic table, a fact that we'll explore in more detail. From a chemical standpoint, selenium can form various types of compounds, including oxoanions, simple anions, and hydrogen anions. These compounds are vital in studying chemical reactions and understanding the behavior of selenium in different environments.
Selenium's role in forming compounds similar to those of sulfur is due to their similar chemical behavior and ability to form analogous structures. This includes forming selenate and selenite ions, which we'll delve into further. Understanding selenium's compound-forming abilities can help in diverse applications from biochemistry to industrial processes.

Periodic Table Group 16

Group 16 of the periodic table, also known as the oxygen group or chalcogens, includes oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and polonium (Po). These elements share some common characteristics due to being in the same column, which affects their chemical reactions and compound formations. The trend in reactivity generally decreases as you go down the group, with oxygen being the most reactive and polonium the least.
One of the reasons elements in Group 16 exhibit similar chemical behaviors is due to having the same number of valence electrons, which is six for all members of this group. This similarity makes it easier for these elements to form compounds with analogous structures, like how selenium forms selenate (SeO_4^{2-}) similarly to sulfur forming sulfate (SO_4^{2-}).
These elements can display different oxidation states, which usually range from -2 to +6, providing them the ability to engage in various types of chemical bonding, including ionic and covalent bonds. This versatility is essential for the formation of diverse compounds observed in both nature and synthetic processes.

Anion Nomenclature

Anions are negatively charged ions, formed when an atom gains one or more electrons. Naming anions is a set process in chemistry, which can vary slightly based on the type of anions. The anion nomenclature includes straightforward rules that greatly aid in understanding chemistry.
For simple anions like (Se^{2-}) , the name typically ends in "-ide," resulting in 'selenide' for selenium. For oxoanions like (SeO_4^{2-}), the name varies based on the amount of oxygen present in the ion; these use suffixes like "-ate" or "-ite." Thus, (SeO_4^{2-}) , which is analogous to sulfate (SO_4^{2-}), is called selenate.
Understanding anion nomenclature is crucial for decoding how different elements bond with one another. As such, it aids in predicting chemical reactions and how anions might interact in biological, geological, or industrial processes.

Chemical Analogies

Chemical analogies involve comparing similar chemical compounds or reactions to understand new or less familiar compounds. Since selenium and sulfur are in the same group in the periodic table, many sulfur compounds have selenium analogs. This similarity aids chemists in predicting the properties and behaviors of selenium compounds.
For example, if you know that (SO_4^{2-}) is called sulfate, you can predict that (SeO_4^{2-}) is called selenate. This same analogy assists in naming selenide (Se^{2-}) and hydrogen selenide ion (HS^-). These analogies are not only helpful for nomenclature but also for understanding the physical and chemical properties of these compounds.
Through analogies, we can also infer other characteristics such as reactivity, solubility, and roles in chemical processes or biological systems. This line of thinking is particularly helpful in academic settings and research, helping connect theoretical concepts with practical observations.

Oxoanions

Oxoanions are polyatomic ions containing oxygen and another element. The general formula includes the element attached to a number of oxygen atoms, and they often carry a charge due to extra or missing electrons. Oxoanions are widespread in both inorganic and organic chemistry, playing roles in industrial processes and natural ecosystems.
Selenium forms several oxoanions similar to sulfur, like selenate (SeO_4^{2-}) and selenite (HSeO_3^- ). These compounds are involved in redox reactions, a central theme in inorganic chemistry, involving the transfer of electrons during chemical reactions.
Understanding oxoanions involves recognizing their structure and oxidation states. This knowledge assists in predicting how these ions will bind with other elements or molecules, and their stability in different environments. Oxoanions also have significance in environmental chemistry, as they can affect the nutritional cycles of ecosystems and influence pollution levels.