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 (b) \(\mathrm{SeO}_{3}^{2-}\) the following ions: (a) \(\mathrm{BrO}_{4}^{-}\), (c) arsenate ion, (d) hydrogen tellurate ion.

Short answer

The chemical formulas for the given ions are: (a) \(\mathrm{BrO}_{4}^{-}\) (as already given), (c) arsenate ion - \(\mathrm{AsO}_{4}^{3-}\), and (d) hydrogen tellurate ion - \(\mathrm{HTeO}_{3}^{-}\).

Step-by-step solution

Finding the pattern for oxyanions

We can use the given oxyanion, \(\mathrm{SeO}_{3}^{2-}\) (selenite ion) as the reference point for our pattern. Selenite ion contains selenium (Se) which belongs to the same group as tellurium (Te), arsenic (As), and bromine (Br). Now we can find the chemical formulas for the other ions.

Finding the chemical formula for (a) \(\mathrm{BrO}_{4}^{-}\)

Since bromine (Br) is right above selenium (Se) in the periodic table, we can expect that bromine would form a similar oxyanion as the selenium (Se) - just with one more oxygen atom and a higher oxidation state. Thus, the chemical formula for bromine-containing oxyanion is already given as \(\mathrm{BrO}_{4}^{-}\).

Finding the chemical formula for (c) arsenate ion

Arsenic (As) is right above selenium (Se) in the periodic table as well. Selenite ion has the chemical formula \(\mathrm{SeO}_{3}^{2-}\), so based on the same pattern as before for bromine, arsenic is likely to form an oxyanion with the same number of oxygens and similar charge. Thus, the chemical formula for the arsenate ion, which is As-containing oxyanion, should be \(\mathrm{AsO}_{4}^{3-}\).

Finding the chemical formula for (d) hydrogen tellurate ion

Tellurium (Te) is right below selenium (Se) in the periodic table, and as before, we can deduce that Te oxyanion should have the same number of oxygen atoms as the Se oxyanion. So the oxyanion should have a formula of \(\mathrm{TeO}_{3}^{2-}\). Now, we need to form the hydrogen tellurate ion, which has one hydrogen (H) atom added to neutralize one negative charge. With that in mind, we can write the chemical formula for hydrogen tellurate ion as \(\mathrm{HTeO}_{3}^{-}\).

Key concepts

Periodic Table

The Periodic Table is a fundamental tool in chemistry, organizing all known elements based on their atomic number as well as other recurring chemical properties. Each column down the table is known as a "group," and elements in the same group often exhibit similar chemical behaviors. This is because they tend to have the same number of valence electrons, which primarily govern how they react with other substances.

• Groups are vertical columns in the periodic table
• Elements in a group have similar valence electron configurations
• They usually form similar compounds, such as oxyanions

For instance, selenium (Se), tellurium (Te), and arsenic (As) all belong to the same group and form oxyanions with similar formulas. Understanding their position helps predict their chemical behavior, like the oxidation states they might exhibit.

Chemical Formula

A chemical formula represents the types and numbers of atoms in a molecule. It’s a concise way to denote chemical substances using the symbols of the elements involved along with numerical subscripts.

• Chemical formulas consist of element symbols and numbers
• The subscript numbers tell you how many atoms of each element are present
• A good chemical formula reflects the compound’s composition

For example, the chemical formula for selenium's oxyanion, selenite ion, is \(\mathrm{SeO}_3^{2-}\). By studying this formula, a chemist can deduce it consists of one selenium atom and three oxygen atoms, carrying an overall charge of 2-. This pattern is similar in related elements like bromine (Br), tellurium (Te), and arsenic (As), guiding us to their respective oxyanion forms.

Oxidation State

The oxidation state (or oxidation number) of an element in a compound reflects its degree of oxidation and is crucial for understanding reaction mechanisms and predicting compound properties.

• Oxidation state denotes the hypothetical charge if electrons were transferred completely
• It helps in balancing redox reactions
• Different elements exhibit various oxidation states depending on their chemical environment

For instance, in an oxyanion like \(\mathrm{SeO}_3^{2-}\), selenium typically exhibits an oxidation state of +4. In contrast, when forming an oxyanion like \(\mathrm{BrO}_4^{-}\), bromine assumes a higher oxidation state of +7. Knowing the common oxidation states of elements helps in predicting their chemical formulas and the types of compounds they will form.