naming ions notes

9.1 Naming Ions >9.1 Naming Ions >

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Chapter 9Chemical Names and Formulas

9.1 Naming Ions

9.2 Naming and Writing Formulas for Ionic Compounds

9.3 Naming and Writing Formulas for Molecular Compounds

9.4 Naming and Writing Formulas forAcids and Bases

9.5 The Laws Governing How Compounds Form

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Ionic compounds consist of a positive metal ion and a negative nonmetal ion combined in a proportion such that their charges add up to a net charge of zero.

• What is the formula of the compound that will be made from Na and Cl?

Monatomic IonsMonatomic Ions

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It is important, in learning the language of chemistry, to be able to name and write the chemical formulas for all ionic compounds.

• The first step is to learn about the ions that form ionic compounds.

• Some ions, called monatomic ions, consist of a single atom with a positive or negative charge resulting from the loss or gain of one or more valence electrons, respectively.

Monatomic IonsMonatomic Ions

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Recall that metallic elements tend to lose valence electrons.

•What is the charge of the aluminum ion?

•What is the charge of the calcium ion?

Monatomic IonsMonatomic Ions

Cations

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• The names of the cations of Group 1A, Group 2A, and Group 3A metals are the same as the name of the metal, followed by the word ion or cation.

• Thus, Na+ is the sodium ion (or cation), Ca2+ is the calcium ion (or cation), and Al3+ is the aluminum ion (or cation).

Monatomic IonsMonatomic Ions

Naming Cations

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Nonmetals tend to gain electrons to form anions, so the charge of a nonmetallic ion is negative.

• What is the charge of the ion formed from the phosphorus atom?

• What is the charge of the ion formed from the fluorine atom?

Monatomic IonsMonatomic Ions

Anions

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Anion names start with the stem of the element name and end in -ide.

• For example, two elements in Group 7A are fluorine and chlorine. The anions for these nonmetals are the fluoride ion (F–) and the chloride ion (Cl–).

Monatomic IonsMonatomic Ions

Naming Anions

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Sample Problem 9.1Sample Problem 9.1

Naming Cations and Anions

Name the ion formed by each of the following elements:

a. potassium

b. oxygen

c. sulfur

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Sample Problem 9.1Sample Problem 9.1

Analyze Identify the relevant concepts.

You can use the periodic table to determine the charge of most Group A elements. •Ions with positive charges are cations;

• Metallic cations take the name of the metal.

•Ions with negative charges are anions. • The names of nonmetallic anions end in

-ide.

1

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Sample Problem 9.1Sample Problem 9.1

Solve Apply concepts to the situation.

Write the symbol for the element.

a. K

b. O

c. S

2

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Sample Problem 9.1Sample Problem 9.1

Solve Apply concepts to the situation.

Determine the charge of the ion formed by the element.

a. K 1+

b. Pb 4+

c. S 2–

2

A negative charge means electrons gained; a positive charge means electrons lost.

9.1 Naming Ions >9.1 Naming Ions >

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Sample Problem 9.1Sample Problem 9.1

Solve Apply concepts to the situation.

Determine whether the ion is a cation or an anion.

a. K 1+ K+ is a cation.

b. O 2 – O2– is an anion.

c. S 2– S2– is an anion.

2

9.1 Naming Ions >9.1 Naming Ions >

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Sample Problem 9.1Sample Problem 9.1

Solve Apply concepts to the situation.

Apply the appropriate rules for naming the ion. Use a Roman numeral if necessary.

a. Following the rules for naming metallic cations, K+ is named potassium ion.

b. Following the rules for naming nonmetallic anions, O2– is named oxide ion.

c. Following the rules for naming nonmetallic anions, S2– is named sulfide ion.

2

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What type of elements (metals or nonmetals) tends to form cations? What type of elements tends to form anions?

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What type of elements (metals or nonmetals) tends to form cations? What type of elements tends to form anions?

Metals tend to form cations. Nonmetals tend to form anions.

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Suppose you were trying to teach someone how to name ions. Which rules about the “language of chemistry” would you emphasize?

Answer this question at the top of INB102.

CHEMISTRY & YOUCHEMISTRY & YOU

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Suppose you were trying to teach someone how to name ions. Which rules about the “language of chemistry” would you emphasize?

CHEMISTRY & YOUCHEMISTRY & YOU

• For cations, the word ion or cation follows the name of the element.

• Metals that form more than one cation are named by adding a Roman numeral in parentheses to indicate the value of the charge after the name of the element, followed by the word ion.

• Anion names start with the stem of the element name and end in -ide.

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Naming Compounds

Name the ionic compounds shown here.

a. MgCl2

b. Li3N

c. Al2S3

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Sample Problem 9.1Sample Problem 9.1

Analyze Identify the relevant concepts.

You can use the periodic table to determine the charge of most Group A elements. •Ions with positive charges are cations;

• Metallic cations take the name of the metal.

•Ions with negative charges are anions. • The names of nonmetallic anions end in

-ide.

1

9.1 Naming Ions >9.1 Naming Ions >

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Sample Problem 9.1Sample Problem 9.1

Solve Apply concepts to the situation.

Write the name of the cations.

a. MgCl2 magnesium

b. Li3N lithium

c. Al2S3aluminum

2

9.1 Naming Ions >9.1 Naming Ions >

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Sample Problem 9.1Sample Problem 9.1

Solve Apply concepts to the situation.

Write the name of the anion.

a. MgCl2 magnesium chloride

b. Li3N lithium nitride

c. Al2S3 aluminum sulfide

2

When naming ionic compounds, ignore the numbers in the

formula.