Formulas and Names of Ionic Compounds

Objectives:

Students will:

• write the name of an ionic compound when given the chemical formula of the compound.

• write the chemical formula of an ionic compound when given the name of the compound.

Why?

Last unit, you learned about the different types of compounds that can be formed by the elements on the periodic table.

Today, we will learn about how different types of compounds are named, starting with ionic compounds.

Part 1: Writing Formulas of Ionic Compounds

Rules for writing the formula for an ionic compound

1. Determine the charge on the metal when it forms a cation.

2. Determine the charge of the nonmetal when it forms an ion.

3. Determine the number of each ion needed to form an neutral compound.

4. Write the element symbol of the metal first, followed by a subscript to show the number of cations in the compound.

5. Write the element symbol of the nonmetal second, followed by a subscript to show the number of anions in the compound.

Note: Never write charges in the formula of a neutral ionic compound.

* Remember, prefixes are only used when the compound is covalent. This is just a reminder of what the different roman numerals represent!

Polyatomic ions are created when a group of atoms come to together to form a compound. In order for those group of atoms to successfully bond together, electrons either had to be lost or gain which results in a charge forming. The list of polyatomic ions below are the ones that will most often be used in class. You can later find these on Schoology in the Resources folder.

Part 2: Naming Ionic Compounds Practice

Rules for naming ionic compounds:

1) Write the name of the cation (+ charged ion).

• IF the cation is a transition metal (a metal located in the d block) you must include a Roman numeral in the name to indicate the charge of the metal.

2) Write the name of the anion.

• IF the anion is a nonmetal changed the ending of the name to -ide. For example, chlorine becomes chloride.

• IF the anion is a polyatomic ion, write the name of the polyatomic ion. Do not change the ending of its name.

Directions: For questions 31-41, write the the name of each of the ionic compounds below.