Question

Name each of the following binary compounds, all of which are composed of a metal and a nonmetal: (a) \(\mathrm{BaO}\) (e) \(\mathrm{Al}_{2} \mathrm{O}_{3}\) (b) \(\mathrm{K}_{2} \mathrm{~S}\) (f) \(\mathrm{CaBr}_{2}\) (c) \(\mathrm{CaCl}_{2}\) (g) \(\mathrm{SrI}_{2}\) (d) \(\mathrm{Cs}_{2} \mathrm{~S}\) (h) \(\mathrm{Mg}_{3} \mathrm{~N}_{2}\)

Short answer

The names are (a) Barium oxide, (b) Potassium sulfide, (c) Calcium chloride, (d) Cesium sulfide, (e) Aluminum oxide, (f) Calcium bromide, (g) Strontium iodide, (h) Magnesium nitride.

Step-by-step solution

- Recognize the Metal and Nonmetal in Each Compound

Identify the metal and nonmetal elements present in each compound. The metal is always named first, followed by the nonmetal with its ending changed to -ide.

- Use Appropriate Naming Conventions

For metals with a fixed oxidation state (Group 1, Group 2, and Aluminum), simply name the metal followed by the nonmetal with an -ide ending. For metals that can have multiple oxidation states, use Roman numerals to indicate the metal's charge if necessary (e.g., iron(III) chloride for FeCl3). However, none of the metals in the given compounds have multiple oxidation states.

- Name Each Compound

For each compound, name the metal first, followed by the nonmetal with an -ide ending. (a) Barium oxide (b) Potassium sulfide (c) Calcium chloride (d) Cesium sulfide (e) Aluminum oxide (f) Calcium bromide (g) Strontium iodide (h) Magnesium nitride.

Key concepts

Chemical Nomenclature

Understanding how to name chemical compounds is essential in the world of chemistry. Chemical nomenclature, the systematic naming of chemical compounds, provides a unique and standardized way for scientists to communicate about compounds. At its core, the process involves identifying the elements within the compound and using specific rules to create its name.

For binary compounds, which consist of two different elements, the rules are relatively straightforward. The first element in the compound’s formula is always named first using its full element name. The second element is named as if it were an anion, meaning its name ends in '-ide.' For instance, chlorine becomes chloride and oxygen becomes oxide when part of a binary compound. This system helps maintain clarity and consistency in naming compounds across the chemical community.

Common Naming Pitfalls to Avoid

It's important to be attentive to details such as spelling and punctuation, as well to the order of the elements. Always start with the cation (usually a metal) followed by the anion (usually a nonmetal or a polyatomic ion). Subscripts in formulas do not affect the base names but may indicate the need to specify oxidation states for certain elements.

Metal and Nonmetal Compounds

Binary compounds are often composed of metals and nonmetals. Metals, which are typically found on the left side of the periodic table, tend to lose electrons to form positive ions called cations. Nonmetals, located on the right side, tend to gain electrons to form negative ions, or anions.

In the binary compounds listed in the exercise, metals such as potassium (K), calcium (Ca), and magnesium (Mg) are paired with nonmetals like sulfur (S), chlorine (Cl), and bromine (Br). When naming these compounds, we reflect the metal followed by the nonmetal's modified name. For example, the compound made of calcium and chlorine is known as calcium chloride.

Significance of Metal and Nonmetal Combinations

The interplay between metals and nonmetals results in the formation of ionic bonds, where electrons are transferred from the metal to the nonmetal. This leads to a compound that has a neutral overall charge but is made up of ions that are charged. Understanding the nature of these bonds gives deeper insight into the complex structures and properties of various compounds in chemistry.

Oxidation States

The oxidation state or oxidation number corresponds to the hypothetical charge an atom would have if all bonds to atoms of different elements were completely ionic. In simple terms, it’s a way of keeping track of an element’s electrons during a reaction and is critical when naming compounds, especially those containing transition metals that can possess multiple possible charges.

For most main group elements, the oxidation state is straightforward and often matches the group number for elements that commonly donate electrons (metallic elements), or the group number subtracted from eight for elements that commonly accept electrons (nonmetals). For example, in the binary compound BaO, barium (Ba) has an oxidation state of +2 and oxygen (O) has an oxidation state of -2, reflecting their charges when they form ions.

Determining Oxidation States

To determine the oxidation state of an element in a compound, start with the knowledge that the sum of oxidation states for all atoms in a neutral compound should equal zero. For ionic compounds, the total positive charges must balance the total negative charges. This helps when naming compounds with transition metals, where the oxidation state is indicated with Roman numerals in parentheses immediately following the metal’s name. In the given examples, all metals have a fixed oxidation state, so additional indicators are not necessary for naming.