3.10: Naming Ionic Compounds

Learning Objectives

• To practice naming ionic compounds by recognizing the ions in the formula.

Naming Compounds

Now that we know how to name ions, we are ready to name ionic compounds. We do so by placing the name of the cation first, followed by the name of the anion, and dropping the word ion from both parts. For example, what is the name of the compound whose formula is \(\ce{Ba(NO3)2}\)?

The compound’s name does not indicate that there are two nitrate ions for every barium ion. You must determine the relative numbers of ions by balancing the positive and negative charges.

If you are given a formula for an ionic compound whose cation can have more than one possible charge, you must first determine the charge on the cation before identifying its correct name. For example, consider \(\ce{FeCl2}\) and \(\ce{FeCl3}\). In the first compound, the iron ion has a 2+ charge because there are two \(\ce{Cl^{−}}\) ions in the formula (1− charge on each chloride ion). In the second compound, the iron ion has a 3+ charge, as indicated by the three \(\ce{Cl^{−}}\) ions in the formula. These are two different compounds that need two different names. By the Stock system, the names are iron(II) chloride and iron(III) chloride. If we were to use the stems and suffixes of the common system, the names would be ferrous chloride and ferric chloride, respectively.

Example \(\PageIndex{3}\)

Name each ionic compound, using both Stock and common systems if necessary.

1. Ca₃(PO₄)₂
2. (NH₄)₂Cr₂O₇
3. KCl
4. CuCl
5. SnF₂

Answer a

calcium phosphate

Answer b

ammonium dichromate (the prefix di- is part of the name of the anion)

Answer c

potassium chloride

Answer d

copper(I) chloride or cuprous chloride

Answer e

tin(II) fluoride or stannous fluoride

Exercise \(\PageIndex{3}\)

Name each ionic compound, using both Stock and common systems if necessary.

1. ZnBr₂
2. Fe(NO₃)₃
3. Al₂O₃
4. CuF₂
5. AgF

Answer a

zinc bromide

Answer b

iron (III) nitrate or ferric nitrate

Answer c

aluminum oxide

Answer d

copper (II) fluoride or cupric fluoride

Answer e

silver fluoride

Figure \(\PageIndex{1}\) is a synopsis of how to name simple ionic compounds.

Figure \(\PageIndex{1}\): A Guide to Naming Simple Ionic Compounds. Follow these steps to name a simple ionic compound.

KEY TAKEAWAY

• Each ionic compound has its own unique name that comes from the names of the ions.

EXERCISES

1. Briefly describe the process for naming an ionic compound.

2. In what order do the names of ions appear in the names of ionic compounds?

3. Which ionic compounds can be named using two different systems? Give an example.

4. Name each ion.

1. Ra²⁺
2. P³⁻
3. H₂PO₄⁻
4. Sn⁴⁺

5. Name each ion.

1. Cs⁺
2. As³⁻
3. HSO₄⁻
4. Sn²⁺

6. Name the ionic compound formed by each pair of ions.

1. Na⁺ and Br⁻
2. Mg²⁺ and Br⁻
3. Mg²⁺ and S²⁻

7. Name the ionic compound formed by each pair of ions.

1. K⁺ and Cl⁻
2. Mg²⁺ and Cl⁻
3. Mg²⁺ and Se²⁻

8. Name the ionic compound formed by each pair of ions.

1. Na⁺ and N³⁻
2. Mg²⁺ and N³⁻
3. Al³⁺ and S²⁻

9. Name the ionic compound formed by each pair of ions.

1. Li⁺ and N³⁻
2. Mg²⁺ and P³⁻
3. Li⁺ and P³⁻

10. Name the ionic compound formed by each pair of ions. Use both the Stock and common systems, where appropriate.

1. Fe³⁺ and Br⁻
2. Fe²⁺ and Br⁻
3. Au³⁺ and S²⁻
4. Au⁺ and S²⁻

11. Name the ionic compound formed by each pair of ions. Use both the Stock and common systems, where appropriate.

1. Cr³⁺ and O²⁻
2. Cr²⁺ and O²⁻
3. Pb²⁺ and Cl⁻
4. Pb⁴⁺ and Cl⁻

12. Name the ionic compound formed by each pair of ions. Use both the Stock and common systems, where appropriate.

1. Cr³⁺ and NO₃⁻
2. Fe²⁺ and PO₄³⁻
3. Ca²⁺ and CrO₄²⁻
4. Al³⁺ and OH⁻

13. Name the ionic compound formed by each pair of ions. Use both the Stock and common systems, where appropriate.

1. NH₄⁺ and NO₃⁻
2. K⁺ and Cr₂O₇²⁻
3. Cu⁺ and CO₃²⁻
4. Na⁺ and HCO₃⁻

14. Give two names for each compound.

1. Al(HSO₄)₃
2. Mg(HSO₄)₂

15. Give two names for each compound.

1. Co(HCO₃)₂
2. LiHCO₃

Answers

1. Name the cation and then the anion but don’t use numerical prefixes.

2. the cation name followed by the anion name

3. Ionic compounds in which the cation can have more than one possible charge have two naming systems. FeCl₃ is either iron(III) chloride or ferric chloride (answers will vary).

4.

1. the radium ion
2. the phosphide ion
3. the dihydrogen phosphate ion
4. the tin(IV) ion or the stannic ion

5.

1. the cesium ion
2. the arsenide ion
3. the hydrogen sulfate ion
4. the tin(II) ion or the stannous ion

6.

1. sodium bromide
2. magnesium bromide
3. magnesium sulfide

7.

1. potassium chloride
2. magnesium chloride
3. magnesium selenide

8.

1. sodium nitride
2. magnesium nitride
3. aluminum sulfide

9.

1. lithium nitride
2. magnesium phosphide
3. lithium phosphide

10.

1. iron(III) bromide or ferric bromide
2. iron(II) bromide or ferrous bromide
3. gold(III) sulfide or auric sulfide
4. gold(I) sulfide or aurous sulfide

11.

1. chromium(III) oxide or chromic oxide
2. chromium(II) oxide or chromous oxide
3. lead(II) chloride or plumbous chloride
4. lead(IV) chloride or plumbic chloride

12.

1. chromium(III) nitrate or chromic nitrate
2. iron(II) phosphate or ferrous phosphate
3. calcium chromate
4. aluminum hydroxide

13.

1. ammonium nitrate
2. potassium dichromate
3. copper(I) carbonate or cuprous carbonate
4. sodium hydrogen carbonate or sodium bicarbonate

14.

1. aluminum hydrogen sulfate or aluminum bisulfate
2. magnesium hydrogen sulfate or magnesium bisulfate

15.

1. cobalt hydrogen carbonate or cobalt bicarbonate
2. lithium hydrogen carbonate or lithium bicarbonate