Question

Elements in the same group of the periodic table often form oxyanions with the same general formula. The anions are also named in a similar fashion. Based on these observations, suggest a chemical formula or name, as appropriate, for each of the following ions: (a) \(\mathrm{BrO}_{4}\) -, (b) \(\mathrm{SeO}_{3}{ }^{2-},(\mathrm{c})\) arsenate ion, (d) hydrogen tellurate ion.

Short answer

The chemical formulas and names for the given ions are: (a) \(\mathrm{BrO}_{4}^-\) is perbromate ion, (b) \(\mathrm{SeO}_{3}{ }^{2-}\) is selenite ion, (c) arsenate ion has the chemical formula \(\mathrm{AsO}_{4}{ }^{3-}\), and (d) hydrogen tellurate ion has the chemical formula \(\mathrm{HTeO}_{4}{ }^{-}\).

Step-by-step solution

Identify the related group element

Bromine (Br) is in Group 17 (Halogens) of the Periodic Table. We will look at another element in the same group, Chlorine (Cl).

Observe the related group element's oxyanion

We observe that ClO₄¯ is perchlorate ion.

Suggest the name for \(\mathrm{BrO}_{4}^-\)

Based on the above observation, we can suggest that \(\mathrm{BrO}_{4}^-\) should be called perbromate ion. (b) \(\mathrm{SeO}_{3}{ }^{2-}\)

Identify the related group element

Selenium (Se) is in Group 16 (Chalcogens) of the Periodic Table. We will look at another element in the same group, Sulfur (S).

Observe the related group element's oxyanion

We observe that SO₃²¯ is called sulfite ion.

Suggest the name for \(\mathrm{SeO}_{3}{ }^{2-}\)

Based on the above observation, we can suggest that \(\mathrm{SeO}_{3}{ }^{2-}\) should be called selenite ion. (c) arsenate ion

Identify the related group element

Arsenic (As) is in Group 15 (Pnictogens) of the Periodic Table. We will look at another element in the same group, Phosphorus (P).

Observe the related group element's oxyanion

We observe that the phosphate ion is \(\mathrm{PO}_{4}{ }^{3-}\).

Suggest the chemical formula for arsenate ion

Based on the above observation, we can suggest that the chemical formula for arsenate ion should be \(\mathrm{AsO}_{4}{ }^{3-}\). (d) hydrogen tellurate ion

Identify the related group element

Tellurium (Te) is in Group 16 (Chalcogens) of the Periodic Table. We will look at another element in the same group, Sulfur (S).

Observe the related group element's oxyanion

We observe that hydrogen sulfate ion is \(\mathrm{HSO}_{4}{ }^{-}\).

Suggest the chemical formula for hydrogen tellurate ion

Based on the above observation, we can suggest that the chemical formula for hydrogen tellurate ion should be \(\mathrm{HTeO}_{4}{ }^{-}\).

Key concepts

Periodic Table Groups

The periodic table is more than just a neat arrangement of elements; it's a powerful tool for predicting their properties and behaviors, including how they form compounds like oxyanions.

Groups, also known as families, are columns of elements in the periodic table. Elements in the same group typically have similar chemical properties, mainly because they have the same number of electrons in their outer shell. This commonality is what guides us in predicting the behavior of elements, particularly when they form ions. For instance, oxyanions such as perchlorate (\(\mathrm{ClO}_{4}^-\)) and perbromate (\(\mathrm{BrO}_{4}^-\)) are formed by elements in Group 17, the halogens. Each group on the periodic table has a unique propensity to form certain types of oxyanions, which makes understanding groups essential when learning to name and write formulas for these ions.

Chemical Nomenclature

Chemical nomenclature is essentially the language of chemistry, providing a system of rules for naming compounds. It may seem like a complex set of rules, but it's actually pretty logical once you get the hang of it.

In the case of polyatomic ions such as oxyanions, their names are generally derived from the name of the element with a specific suffix ('-ate' or '-ite') and sometimes a prefix ('per-' or 'hypo-') to indicate the number of oxygen atoms present. For instance, 'perchlorate' refers to the chlorine oxyanion with the most oxygen atoms (\(\mathrm{ClO}_{4}^-\)), while 'chlorite' would have fewer (
\(\mathrm{ClO}_{2}^-\)). Understanding these naming conventions is critical for students to communicate accurately in the world of inorganic chemistry.

Inorganic Chemistry

Inorganic chemistry is all about the study of inorganic compounds, which, unlike organic compounds, do not contain carbon-hydrogen (C-H) bonds. Many inorganic compounds are made up of a metallic or semi-metallic element combined with various nonmetals, including oxygen, which leads us to oxyanions.

These anions are ubiquitous components of various chemical reactions, especially in the field of analytical chemistry, where understanding the composition and nomenclature of these ions becomes exceedingly important for students. Knowing how elements from different groups on the periodic table behave helps chemists predict and understand the structures and reactivity of inorganic compounds.

Polyatomic Ions

Polyatomic ions are ions with two or more atoms bonded together that carry a net electrical charge. Oxyanions, a subset of polyatomic ions, include one or more oxygen atoms bonded to a central atom.

The naming for these ions is not random; it involves understanding both the number of oxygen atoms and the oxidation state of the central atom. For example, nitrate (\(\mathrm{NO}_{3}^{-}\)) and nitrite (\(\mathrm{NO}_{2}^{-}\)) are both ions consisting of nitrogen and oxygen, but they differ in the number of oxygen atoms. Learning to recognize and name these ions correctly is a crucial part of mastering chemical nomenclature, paving the way for successful work in inorganic chemistry and beyond.