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Write the names for ionic compounds, molecular compounds, polyatomic ions, and acids by interpreting their formulas.

1. Read the formula and look at the subscripts.

Li2O

Note that Li is a metal and O is a nonmetal, which can be determined by referencing a periodic table like the one in Figure 1.

2. Determine if the metal ion has a fixed charge or variable charge.

Li = Group IA = fixed charge = 1+

3. Record the entire name of the cation.

Li = lithium

4. Write the root name of the nonmetal ion with the suffix “-ide.”

O = oxygen = oxide

5. Write the name of the ionic compound.

lithium oxide

Example 6: Writing a Metal + Nonmetal Name: Fe2O3 1. Read the formula and look at the subscripts.

Fe2O3 2. Determine if the metal ion has a fixed charge or variable charge.

Fe = Group VIIIB = variable charge = 2+ or 3+

3. Record the entire name of the cation.

Fe = iron

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Experiment Naming Ionic and Molecular Compounds

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Experiment Naming Ionic and Molecular Compounds

4. Determine the Roman numeral by balancing the charges to create a neutral compound.

a. There are 2 atoms of iron and 3 atoms of oxygen.

b. We know oxygen always carries a 2- charge so all 3 atoms of oxygen have a 2- charge.

c. We need to determine if each iron atom has a 2+ or a 3+ charge by a simple algebraic calculation where the charge for each iron atom equals x and the equation is set to 0:

Tip: To balance Fe2O3, first consider the oxygen atoms. Oxygen always has a charge of 2-, therefore O3 has a total charge of 6-. This means that Fe2 must have a total charge of 6+. Each F atom will have a charge of 3+.

d. After solving for x, we find that each iron atom carries a 3+ charge. Thus, the Roman numeral used in the compound name is “III.”

iron(III)