Question

In each of the following, identify which names are incorrect for the given formulas, and give the correct name. a. \(\mathrm{CuCl}_{2}\), copper(I) chloride b. \(\mathrm{Ag}_{2} \mathrm{O},\) silver oxide c. \(\mathrm{Li}_{2} \mathrm{O},\) lithium oxide d. CaS , calcium(II) sulfide e. \(\mathrm{Cs}_{2} \mathrm{~S}\), cesium sulfide

Short answer

The incorrect name is copper(I) chloride for \(\mathrm{CuCl}_{2}\). The correct name should be copper(II) chloride. All other given names are correct.

Step-by-step solution

Identify incorrect names

We will go through each part of the exercise and determine which chemical names are incorrect by analyzing the charges on each compound. a. \(\mathrm{CuCl}_{2}\), copper(I) chloride b. \(\mathrm{Ag}_{2} \mathrm{O},\) silver oxide c. \(\mathrm{Li}_{2} \mathrm{O},\) lithium oxide d. CaS , calcium(II) sulfide e. \(\mathrm{Cs}_{2} \mathrm{~S}\), cesium sulfide

Determine the correct names

Now, we will provide the correct names for each compound for which the given name was incorrect: a. \(\mathrm{CuCl}_{2}\), copper(I) chloride The charges are incorrect here. Copper has a charge of +2 and chlorine has a charge of -1, thus the correct name should be copper(II) chloride. b. \(\mathrm{Ag}_{2} \mathrm{O},\) silver oxide The charges are correct here. Silver has a charge of +1 and oxygen has a charge of -2. Since we have two silver atoms, the charges balance out. Thus, the given name silver oxide is correct. c. \(\mathrm{Li}_{2} \mathrm{O},\) lithium oxide The charges are correct here as well. Lithium has a charge of +1 and oxygen has a charge of -2. As we have two lithium atoms, the charges balance out, and the given name lithium oxide is correct. d. CaS , calcium(II) sulfide The charges are correct here too. Calcium has a charge of +2 and sulfur has a charge of -2, resulting in a balanced ionic compound. The given name, calcium(II) sulfide, is correct. e. \(\mathrm{Cs}_{2} \mathrm{~S}\), cesium sulfide The charges are correct here. Cesium has a charge of +1 and sulfur has a charge of -2. Since we have two cesium atoms, the charges balance out. Thus, the given name, cesium sulfide, is correct. So, the only incorrect name is in the part (a), where the correct name should be copper(II) chloride.

Key concepts

Ionic Compound Naming

Understanding the naming conventions for ionic compounds is essential for students studying chemistry. Ionic compounds consist of cations (positively charged ions) and anions (negatively charged ions). The key rule for naming ionic compounds is to write the name of the cation first, followed by the name of the anion. For cations that can have more than one charge, such as transition metals, a Roman numeral in parentheses indicates the cation's charge.

For example, in the compound \(\mathrm{CuCl}_{2}\), copper is the cation and chlorine is the anion. Since copper can have multiple charges, it is important to specify its charge in the name. The incorrect name given, copper(I) chloride, suggests that copper has a +1 charge, which cannot be the case as chlorine always has a -1 charge and there are two chloride ions. The correct name, therefore, is copper(II) chloride, indicating that copper has a +2 charge.

Valency of Elements

The valency of an element is a measure of its ability to combine with other atoms. It is determined by the number of electrons an atom can lose, gain, or share to attain a full valence electron shell. In ionic compounds, the total positive charge of the cations must balance the total negative charge of the anions.

When naming an ionic compound, the valency plays a crucial role. For instance, calcium (Ca) has a valency of +2 and will pair with sulfur (S), which has a valency of -2, to form calcium sulfide (CaS). The valency must be considered to correctly name the compound, especially in a situation where the metal can have more than one valency. This principle is used in determining the correct names of ionic compounds and ensuring their charges balance.

Correct Chemical Names

Providing the correct chemical names for compounds is an important skill in chemistry communication. Incorrect names can lead to confusion or misinformation. To arrive at the correct name, one must consider the valency of the elements and the ratio in which they combine. The compound \(\mathrm{Cs}_{2} \mathrm{~S}\), correctly named cesium sulfide, shows a 2:1 ratio of cesium to sulfur ions, reflecting the charges of +1 for cesium and -2 for sulfur, respectively. Correct names often also include the oxidation state for elements that can have more than one charge, such as transition metals, to avoid ambiguity.

Use of systematic nomenclature rules benefits not only academic purposes but also professional and industry-related communication, ensuring that everyone speaks the same chemical language.