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9.1 Naming Ions >

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Chapter 9 Chemical 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 for Acids and Bases 9.5 The Laws Governing How Compounds Form

9.1 Naming Ions >

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9.1 Naming Ions >


Try looking at the ingredient label on a household product—a bottle of shampoo, a tube of toothpaste, a box of detergent. Do the names of the ingredients make sense?

CHEMISTRY & YOU

Do you speak “Chemistry”?

9.1 Naming Ions >


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.

• For example, the ionic compound

sodium chloride (NaCl) consists of one sodium ion (Na+) and one chloride ion (Cl–).

Monatomic Ions

9.1 Naming Ions >


• 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 Ions

9.1 Naming Ions >


Recall that metallic elements tend to lose valence electrons.

• All the Group 1A ions have a 1+ charge (Li+, Na+, K+, Rb+, and Cs+).

• Group 2A metals, including magnesium and

calcium, tend to lose two electrons to form cations with a 2+ charge (Mg2+ and Ca2+).

• Aluminum a Group 3A metal, tends to lose three electrons to form a 3+ cation (Al3+).

Monatomic Ions

Cations

9.1 Naming Ions >


When the metals in Groups 1A, 2A, and 3A lose electrons, they form cations with positive charges equal to their group number.

Monatomic Ions

Cations

9.1 Naming Ions >


• 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 Ions

Cations

9.1 Naming Ions >

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• What would be the charge and the name of the ions formed by the following?

• Lithium

• Phosphorous

• Gallium Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

9.1 Naming Ions >


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

Monatomic Ions

Anions

9.1 Naming Ions >


The charge of any ion of a Group A nonmetal is determined by subtracting 8 from the group number.

Monatomic Ions

Anions

9.1 Naming Ions >


The charge of any ion of a Group A nonmetal is determined by subtracting 8 from the group number. The elements in Group 7A form anions with a 1– charge (7 – 8 = –1).

Monatomic Ions

Anions

9.1 Naming Ions >


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 Ions

Anions

9.1 Naming Ions >


Anions of nonmetals in Group 6A have a 2– charge (6 – 8 = –2).

• Group 6A elements, oxygen and sulfur,

form the oxide anion (O2–) and the sulfide anion (S2–), respectively.

Monatomic Ions

Anions

9.1 Naming Ions >


The first three elements in Group 5A, nitrogen, phosphorus, and arsenic, can form anions with a 3– charge (5 – 8 = –3).

• These anions have the symbols N3–,

P3–, and As3– and are called, respectively, nitride ion, phosphide ion, and arsenide ion.

Monatomic Ions

Anions

9.1 Naming Ions >

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• What is the charge and name of the ion formed from the following?

• Nitrogen

• Sulfur

• Bromine

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9.1 Naming Ions >


Many of the transition metals (Groups 1B–8B) form more than one cation with different ionic charges. Some are shown at right.

Monatomic Ions

Metals That Form More Than One Ion

9.1 Naming Ions >


The charges of the cations of many transition metal ions must be determined from the number of electrons lost.

Monatomic Ions


9.1 Naming Ions >


The charges of the cations of many transition metal ions must be determined from the number of electrons lost.

• For example, the transition metal iron forms two common cations, Fe2+ (two electrons lost) and Fe3+ (three electrons lost).

• Cations of tin and lead, the two metals in Group 4A, can also have more than one common ionic charge.

Monatomic Ions


9.1 Naming Ions >


Metals That Form More Than One Ion Two methods are used to name ions that can have more than one common ionic charge.

• The preferred method is called the Stock system.

Monatomic Ions

9.1 Naming Ions >


In the Stock system, you place a Roman numeral in parentheses after the name of the element to indicate the numerical value of the charge.

• For example, the cation Fe2+ is named iron(II) ion and is read “iron two ion.”

• No space is left between the element name and the Roman numeral in parentheses.

• The Fe3+ ion is named iron(III) ion and is read “iron three ion.”

Monatomic Ions


9.1 Naming Ions >


An older, less useful method for naming these cations uses a root word with different suffixes at the end of the word.

• The older, or classical, name of the element is used to form the root name for the element. • For example, ferrum is Latin for iron,

so ferr- is the root name for iron.

Monatomic Ions


9.1 Naming Ions >


An older, less useful method for naming these cations uses a root word with different suffixes at the end of the word.

• The suffix -ous is used to name the cation with the lower of the two ionic charges.

• The suffix -ic is used with the higher of the two ionic charges.

• Using this system, Fe2+ is the ferrous ion, and Fe3+ is the ferric ion.

Monatomic Ions


9.1 Naming Ions >


You can usually identify an element from what may be an unfamiliar classical name by looking for the element’s symbol in the name.

• For example, ferrous (Fe) is iron, cuprous (Cu) is copper, and stannous (Sn) is tin.

Monatomic Ions


9.1 Naming Ions >


Monatomic Ions

A major disadvantage of using classical names for ions is that they do not tell you the actual charge of the ion.

Symbols and Names of Common Metal Ions With More Than One Ionic Charge

Symbol Stock Name Classical Name Cu2+ Copper(I) ion Cuprous ion

Cu2+ Copper(II) ion Cupric ion

Pb2+ Lead(II) ion Plumbous ion

Pb4+ Lead(IV) ion Plumbic ion

9.1 Naming Ions >


Sample Problem 9.1

Naming Cations and Anions

Name the ion formed by each of the following elements and write the symbol with the correct charge.

a. potassium

b. lead, 4 electrons lost

c. Aluminum

d.Sulfur

9.1 Naming Ions >

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• Name the ion formed by each of the following elements. Write the symbol with the correct charge

• Iron 3 electrons lost • Calcium • Copper 1 electron lost • Fluorine

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9.1 Naming Ions >


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

9.1 Naming Ions >


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.

9.1 Naming Ions >


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

CHEMISTRY & 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.

9.1 Naming Ions >


Unlike a monatomic ion, a polyatomic ion is composed of more than one atom. But like a monatomic ion, a polyatomic ion behaves as a unit and carries a charge.

Polyatomic Ions

9.1 Naming Ions >


• The sulfate anion consists of one sulfur atom and four oxygen atoms. • These five atoms together comprise a

single anion with an overall 2– charge.

• The formula is written SO42–.

Polyatomic Ions

9.1 Naming Ions >


You can see the structure of the sulfate ion along with three other common polyatomic ions below.

Polyatomic Ions

Ammonium ion (NH4

+) Nitrate ion

(NO3–)

Sulfate ion (SO4

2–) Phosphate ion

(PO43–)

9.1 Naming Ions >


The names and formulas of some common polyatomic ions are shown here. Note that the names of most polyatomic ions end in -ite or -ate.

Polyatomic Ions

Common Polyatomic Ions Charge Formula Name

1– HSO4

–

NO2–

ClO–

Hydrogen sulfate Nitrite Hypochlorite

2– SO3

2–

SO42–

CO32–

Sulfite Sulfate Carbonate

3– PO43– Phosphate

1+ NH4+ Ammonium

9.1 Naming Ions >


For example, notice the endings of the names of the hypochlorite ion (ClO–) and the carbonate ion (CO3

–).

Polyatomic Ions

Common Polyatomic Ions Charge Formula Name

1– HSO4

–

NO2–

ClO–

Hydrogen sulfate Nitrite Hypochlorite

2– SO3

2–

SO42–

CO32–

Sulfite Sulfate Carbonate

3– PO43– Phosphate

1+ NH4+ Ammonium

9.1 Naming Ions >


The hydrogen carbonate anion (HCO3–), the

hydrogen phosphate anion (HPO42–), and

the dihydrogen phosphate anion (H2PO42–)

are essential components of living systems.

Polyatomic Ions

The presence of these ions dissolved in your blood is critical for your health.

9.1 Naming Ions >


Sodium hydrogen carbonate, which contains the HCO3

– ion, can relieve an upset stomach.

Polyatomic Ions

In contrast, the cyanide ion (CN–) is extremely poisonous to living systems because it blocks a cell’s means of producing energy.

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