Question

Name each of the following compounds: a. CuI b. \(\mathrm{CuI}_{2}\) c. \(\mathrm{CoI}_{2}\) d. \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) e. \(\mathrm{NaHCO}_{3}\) f. \(\mathrm{S}_{4} \mathrm{~N}_{4}\) g. \(\mathrm{SeCl}_{4}\) h. \(\mathrm{NaOCl}\) i. \(\mathrm{BaCrO}_{4}\) j. \(\mathrm{NH}_{4} \mathrm{NO}_{3}\)

Short answer

a. Copper(I) iodide b. Copper(II) iodide c. Cobalt(II) iodide d. Sodium carbonate e. Sodium bicarbonate f. Tetrasulfur tetranitride g. Selenium tetrachloride h. Sodium hypochlorite i. Barium chromate j. Ammonium nitrate

Step-by-step solution

a. CuI

This compound consists of copper (Cu) and iodide (I). Copper typically has oxidation states of +1 or +2. Since the charge on iodide is -1, the copper must have an oxidation state of +1 in this compound. Therefore, the compound name is copper(I) iodide.

b. \(\mathrm{CuI}_{2}\)

This compound consists of copper (Cu) and two iodide ions (I). The total charge on the two iodide ions is -2, so the copper must have an oxidation state of +2. Hence, the compound name is copper(II) iodide.

c. \(\mathrm{CoI}_{2}\)

This compound consists of cobalt (Co) and two iodide ions (I). Since the total charge on the two iodide ions is -2, the cobalt must have an oxidation state of +2. Therefore, the compound name is cobalt(II) iodide.

d. \(\mathrm{Na}_{2} \mathrm{CO}_{3}\)

This compound contains two sodium ions (Na) and a carbonate ion (\(\mathrm{CO}_{3}\)). Sodium has an oxidation state of +1, and the carbonate ion has a charge of -2. Therefore, the compound name is sodium carbonate.

e. \(\mathrm{NaHCO}_{3}\)

This compound contains a sodium ion (Na), a hydrogen ion (H), and a bicarbonate ion (\(\mathrm{HCO}_{3}\)). The compound name is sodium bicarbonate.

f. \(\mathrm{S}_{4} \mathrm{~N}_{4}\)

This compound is a covalent compound (instead of an ionic one) and consists of four sulfur atoms (S) bonded to four nitrogen atoms (N). The compound name is tetrasulfur tetranitride.

g. \(\mathrm{SeCl}_{4}\)

This compound is also a covalent compound and consists of selenium (Se) bonded to four chlorine atoms (Cl). The compound name is selenium tetrachloride.

h. \(\mathrm{NaOCl}\)

This compound contains a sodium ion (Na) and a hypochlorite ion (\(\mathrm{OCl}\)). The compound name is sodium hypochlorite.

i. \(\mathrm{BaCrO}_{4}\)

This compound contains barium (Ba) and a chromate ion (\(\mathrm{CrO}_{4}\)). The compound name is barium chromate.

j. \(\mathrm{NH}_{4} \mathrm{NO}_{3}\)

This compound contains the ammonium ion (\(\mathrm{NH}_{4}\)) and the nitrate ion (\(\mathrm{NO}_{3}\)). The compound name is ammonium nitrate.

Key concepts

Oxidation States

In chemistry, the oxidation state, also called oxidation number, is an indicator of the degree of oxidation of an atom that is part of a compound. Understanding oxidation states is crucial when naming chemical compounds, particularly for elements that can have more than one possible charge, like copper in the provided exercise.

For example, in the compound copper(I) iodide, denoted as CuI, copper has an oxidation state of +1. This tells us that each copper atom donates one electron to form the compound. Similarly, in copper(II) iodide or \(\mathrm{CuI}_{2}\), copper has an oxidation state of +2, indicating that it has lost two electrons. These oxidation states are indicated in parentheses in the compound's name to avoid ambiguity and provide precise chemical information.

Ionic Compounds

Ionic compounds are formed by the electrostatic attraction between positively charged ions, called cations, and negatively charged ions, known as anions. When naming ionic compounds, it's important to identify the ions involved and their oxidation states. For instance, sodium carbonate (\(\mathrm{Na}_{2} \mathrm{CO}_{3}\)) is an ionic compound consisting of sodium ions (Na⁺) and a carbonate ion (\(\mathrm{CO}_{3}^{2-}\)) coming together to form a neutral compound.

In the context of your textbook exercise, recognizing whether a substance is ionic helps determine the appropriate naming convention. Usually, the name of the ionic compound is simply the name of the cation followed by the name of the anion.

Covalent Compounds

In contrast to ionic compounds, covalent compounds consist of atoms sharing electrons in bonds rather than exchanging them. The compound tetrasulfur tetranitride (\(\mathrm{S}_{4} \mathrm{~N}_{4}\)) is an excellent example featuring covalent bonds. Here, four sulfur atoms bond covalently with four nitrogen atoms.

When naming covalent compounds, prefixes are used to indicate the number of each type of atom present. For example, the 'tetra-' in tetrasulfur tetranitride signifies four atoms of each element. Understanding the prefixes used for covalent compounds is essential for accurate communication in chemistry.

Polyatomic Ions

Polyatomic ions are charged entities composed of two or more covalently bonded atoms. These ions cannot be simply named by their component elements because they have characteristic names that denote their specific structures and properties. For example, in the compound sodium bicarbonate (\(\mathrm{NaHCO}_{3}\)), the bicarbonate ion (\(\mathrm{HCO}_{3}^{-}\)) is the polyatomic ion.

Common polyatomic ions found in your exercise include carbonate (\(\mathrm{CO}_{3}^{2-}\)), hypochlorite (\(\mathrm{OCl}^{-}\)), chromate (\(\mathrm{CrO}_{4}^{2-}\)), and nitrate (\(\mathrm{NO}_{3}^{-}\)). Remembering these polyatomic ions and their corresponding names is key to correctly naming compounds they feature in.