Question

Explain how to name binary ionic compounds. How do you name an ionic compound if it contains a polyatomic ion?

Short answer

For binary ionic compounds, name the metal cation followed by the non-metal anion with the suffix '-ide'. If the compound contains a polyatomic ion, name the cation followed by the polyatomic ion without changing its name.

Step-by-step solution

Identifying the Ions

Binary ionic compounds consist of two elements: a metal (cation) and a non-metal (anion). Identify the metal which will be written first and the non-metal which will be second in the compound's formula.

Naming the Metal (Cation)

Name the metal as it appears on the periodic table. If the metal has more than one possible ionic charge, use Roman numerals in parentheses to indicate the charge of the metal ion.

Naming the Non-Metal (Anion)

Name the non-metal by taking its root name and adding the suffix '-ide'. For example, chloride for chlorine, oxide for oxygen, etc.

Naming Compounds with Polyatomic Ions

For compounds containing polyatomic ions, first identify the polyatomic ion. Name the compound by stating the cation first, followed by the polyatomic ion as it is named in the list of common polyatomic ions. Do not change the name of the polyatomic ion.

Write the Full Compound Name

Combine the names of the cation and anion (including the polyatomic ion if present) to write the full name of the compound. If using Roman numerals for the cation charge, place them immediately after the cation name without spaces.

Key concepts

Polyatomic Ions

Understanding polyatomic ions is a crucial aspect of mastering the naming of binary ionic compounds. These ions are composed of two or more atoms bonded together, carrying an overall charge. Unlike monatomic ions, which are formed from single atoms, polyatomic ions behave as a single unit and retain their identity during chemical reactions.

For instance, the sulfate ion (\(SO_4^{2-}\)) consists of one sulfur atom connected to four oxygen atoms. Despite being made of several atoms, it acts like a single negatively charged ion. When naming an ionic compound that contains a polyatomic ion, you must recognize the polyatomic ion from the list of common polyatomic ions and use its established name without alteration. This contrasts with naming simple anions, where the suffix '-ide' is added to the root of the element's name.

Chemical Nomenclature

The process of naming chemicals is systematized through chemical nomenclature. It is a set of rules to generate systematic names for chemical compounds. Accurate communication in the field of chemistry hinges on the universal understanding of these names. Naming binary ionic compounds demands an understanding of the components: a positive cation and a negative anion.

Following the exercise improvement advice, when you encounter a cation with a variable charge, such as iron (Fe), it is imperative to identify its precise charge in the specific compound and indicate it with Roman numerals in the compound's name. For example, iron(III) chloride indicates that iron has a +3 charge in this compound. On the other hand, simple cations, like sodium (Na), always have the same charge and are named directly after the element without additional indicators.

Ionic Charge

The concept of ionic charge is integral to writing the formulas and naming ionic compounds. An ion is an atom or a group of atoms with a net electric charge due to the loss or gain of one or more electrons. Metals tend to lose electrons, forming positive cations, while non-metals tend to gain electrons, forming negative anions.

When naming an ionic compound, the sum of the charges must balance, totaling zero. For example, in sodium chloride (\(NaCl\)), sodium (\(Na^+\)) and chloride (\(Cl^-\)) ions have equal and opposite charges that cancel each other out. In cases where there are multiple ions, you must adjust the numbers of each ion so that the overall charge is neutral. Recognizing the charge helps not only in naming the compound accurately but also in understanding its chemical properties and behavior in reactions.