Question

Although relatively rare, all of the following compounds exist. Based on what you know about related compounds (for example, from the periodic table), propose a plausible name or formula for each compound: (a) silver(I) astatide; (b) \(\mathrm{Na}_{4} \mathrm{XeO}_{6} ;\) (c) magnesium polonide; (d) \(\mathrm{H}_{2} \mathrm{TeO}_{3} ;\) (e) potassium thioselenate; (f) \(\mathrm{KAtO}_{4}\).

Short answer

The compounds are: (a) silver(I) astatide - \(\mathrm{AgAt}\)(b) \(\mathrm{Na}_{4} \mathrm{XeO}_{6}\) - sodium hexaoxenon(IV) (c) magnesium polonide - \(\mathrm{MgPo}\)(d) \(\mathrm{H}_{2} \mathrm{TeO}_{3}\) - hydrotelluric acid(e) potassium thioselenate - \(\mathrm{K}_{2}\mathrm{SeO}_3\)(f) \(\mathrm{KAtO}_{4}\) - potassium perastatate.

Step-by-step solution

Naming silver(I) astatide

To name a compound, we need to write the metal first (silver in this case) and then the non-metal (astatide here), changing the ending to -ide. Now, the formula would be \(\mathrm{AgAt}\). Silver(I) indicates that the silver ion has a +1 charge, and astatide is a halogen that forms a -1 ion. Therefore, it takes one of each to balance the charges.

Naming \(\mathrm{Na}_{4} \mathrm{XeO}_{6}\)

Here, we have a compound of sodium (Na), xenon (Xe) and oxygen (O). The roman numeral (or subscript) is not mentioned here because these ions have a fixed oxidation number, unlike transition elements. Using simple rules for aqueous ionic compounds, we can name this compound as sodium hexaoxenon(IV).

Naming magnesium polonide

In this case, magnesium is a group 2 element and hence has a +2 charge, and polonide (from polonium) is a group 16 element and hence forms a -2 ion. To balance these charges, we need one of each atom, thus the formula would be \(\mathrm{MgPo}\). The compound is a binary ionic compound composed of magnesium and polonium.

Naming \(\mathrm{H}_{2} \mathrm{TeO}_{3}\)

This compound is a ternary compound, since it is composed of three types of elements: hydrogen (H), tellurium (Te), and oxygen (O). From the structure, it can be seen that this compound is a type of acid. The name of this compound, applying the rules of nomenclature, would be hydrotelluric acid.

Naming potassium thioselenate

This is a ternary ionic compound. Here potassium sits in group 1 of the periodic table and has a +1 charge. Selenium and oxygen are part of the polyatomic ion thioselenate (\(\mathrm{SeO}_{3}^{2-}\)). Since the polyatomic ion has a -2 charge, we need two potassium ions to balance the charge. Thus the formula is \(\mathrm{K}_{2}\mathrm{SeO}_3\).

Naming \(\mathrm{KAtO}_{4}\)

This is a ternary ionic compound. Potassium is in group 1 of the periodic table and has a +1 charge, while astatine and oxygen are part of the polyatomic ion perastatate (\(\mathrm{AtO}_{4}^{-}\)). Hence to balance the charge, we need one potassium ion. Thus the compound can be named as potassium perastatate.

Key concepts

Understanding the Periodic Table

The periodic table is a systematic arrangement of elements, ordered by their atomic number, electron configurations, and recurring chemical properties. This table forms the cornerstone of modern chemistry and plays a crucial role in the study of chemical nomenclature.

Elements are grouped into rows called periods and columns known as groups or families. Elements within the same group typically exhibit similar chemical behaviors. For instance, all alkali metals (in group 1) are highly reactive and form +1 ions. Similarly, the halogens (in group 17) are known for forming -1 ions.

Understanding the location of an element on the periodic table can provide insights into its reactions and bonding patterns. This information is vital when naming compounds, as the valency and ionic charges of elements are essential in determining the correct formula. For example, if we take silver (Ag) and astatine (At), knowing that silver forms a +1 ion and astatine forms a -1 ion lets us deduce that they can combine to form the compound AgAt, named silver(I) astatide.

Ionic Compounds and Their Formation

Ionic compounds are formed when metal and non-metal atoms exchange electrons, resulting in a compound made up of positively charged ions (cations) and negatively charged ions (anions). The metal loses electrons to become a cation, while the non-metal gains electrons to become an anion.

The overarching rule is that the total positive charge must balance the total negative charge, leading to a neutral compound. In the example of magnesium polonide (MgPo), magnesium is in group 2 and forms a +2 ion, while polonium is in group 16 and tends to form a -2 ion. One atom of magnesium bonds with one atom of polonium to produce a neutrally charged compound due to the canceling out of charges.

In chemical nomenclature for ionic compounds, the cation (metal) is named first, followed by the anion (non-metal), with the non-metal's ending typically changed to '-ide'. If the metal can have multiple charges, a Roman numeral in parentheses indicates its charge, as seen in the naming of sodium hexaoxenon(IV) from the compound \(\mathrm{Na}_{4} \mathrm{XeO}_{6}\).

Polyatomic Ions and Their Integration in Compounds

Polyatomic ions are ions composed of two or more atoms covalently bonded together that carry a net charge. They can be considered as a single charged entity when combining with other ions to form ionic compounds. In simple terms, they're like a team working together under a single charge.

Common polyatomic ions include sulfate (\(\mathrm{SO}_{4}^{2-}\)), nitrate (\(\mathrm{NO}_{3}^{-}\)), and as demonstrated in the alkaline earth compound potassium thioselenate (\(\mathrm{K}_{2}\mathrm{SeO}_3\)), the ion thioselenate (\(\mathrm{SeO}_{3}^{2-}\)). Understand that for nomenclature, the name of the polyatomic ion is maintained within the name of the compound, which helps reflect its distinct chemical identity.

Potassium perastatate is another example where potassium (K+), a group 1 element, pairs with the polyatomic ion perastatate (\(\mathrm{AtO}_{4}^{-}\)) to form an ionic compound. In naming compounds with polyatomic ions, the importance of knowing both the ion's charge and the overall neutrality of the compound is emphasized, guiding the proportion of each ion required for the compound's formation.