Chapter 10 & 7A

Ions

Monatomic Ions

Ion Formulas and Names

Ion Vocabulary• An ion is an atom or group of

atoms that have a charge.

• A cation is a positive ion.

• An anion is a negative ion.

If a neutral atom loses one or more electrons it becomes a cation.

If a neutral atom gains one or more electrons it becomes an anion.

Na11 protons11 electrons Na+

11 protons10 electrons

Cl17 protons17 electrons Cl-

17 protons18 electrons

2.5

Atoms tend to lose and gain electrons when they bond with other

atoms in an attempt to become more stable.

Why is Na+ more stable than Na

• Na = 1s22s22p63s1

Why is Na+ more stable than Na

• Na = 1s22s22p63s1

Lose 1 e-

• Na+ = 1s22s22p6

Why is Na+ more stable than Na

• Na = 1s22s22p63s1

Lose 1 e-

• Na+ = 1s22s22p6

• This is isoelectronic with Ne

Why is Clˉ more stable than Cl

• Cl = 1s22s22p63s23p5

Why is Clˉ more stable than Cl

• Cl = 1s22s22p63s23p5

Gain 1 e-

• Clˉ = 1s22s22p63s23p6

Why is Clˉ more stable than Cl

• Cl = 1s22s22p63s23p5

Gain 1 e-

• Clˉ = 1s22s22p63s23p6

• This is isoelectronic with Ar

Determine the number of protons and electrons for each ion and state what noble

gas each is isoelectronic with.

Mg12 protons12 electrons Mg2+ ___ protons

___ electrons___ isoelectronic

O 8 protons8 electrons O2-

___ protons___ electrons___ isoelectronic

Ionic bonding: Li + OIonic bonding: Li + O

1e-

[ O ]2–[Li]2+

6e- 2e-

8n0 8p+

1e-

3p+

4n02e-1e-

3p+

4n02e-1e-

8e- 2e-

8n0 8p+

3p+

4n02e-

3p+

4n02e-

Why is lithium oxide Li2O

OLi

Li

Ion Vocabulary• A monatomic ion is an atom

with a charge.

• The charge on a monatomic ion is called an oxidation number.

• A polyatomic ion is a group of atoms with a charge.

Types of monatomic ions and the rules for naming them

• The periodic table is useful in naming the monatomic ions.

Monatomic cations with one oxidation number

• The cations from the periodic table which have a single oxidation number are as follows: Group 1 (+1), Group 2 (+2), Ag+, Cd2+, Zn2+, and Al3+.

• These types of ions are named by using the name of the element followed by the word ion.

• Na+ sodium ion• Ba2+ barium ion• Zn2+ zinc ion

• We can use the roman numeral from the periodic table to identify the oxidation number for these ions.

Monatomic cations with multiple oxidation numbers• All other cations that are not listed in the previous

category (“cations with one oxidation number”) are considered to have the possibility of multiple oxidation numbers.

• These type of ions are named by using the name of the element followed by a Roman numeral to indicate the oxidation number.

• Cu2+ copper (II)• Pb4+ lead (IV)• Mn7+ manganese (VII)

• It is important to note that the roman numerals in these names may or may not be the roman numeral from the periodic table. In other words the periodic table is of little or no help in determining their oxidation numbers.

Monatomic anions• All anions from the periodic table are

named by changing the ending of the element’s name to –ide.

• F- fluoride ion

• O2- oxide ion

• N3- nitride ion

• Count back from the noble gases starting at zero to determine the oxidation number.

Name these monatomic ions

• Rb+

• P3-

• Fe3+

• Br‾

• Mn4+

• Cd2+

Rubidium ion

Phosphide

Iron III

Bromide

Manganese IV

Cadmium ion

Write the formula for these monatomic ions.

• Sulfide

• Lead (II)

• Barium ion

• Chromium (IV)

• Aluminum ion

• Carbide

S2-

Pb2+

Ba2+

Cr4+

Al3+

C4-

Atoms of elements and Ions of elements are different

Atoms of elements

A pale yellow-green gas, chlorine killed soldiers in WWI. Today it mainly purifies drinking water and swimming pools.

Sodium is a soft, silvery highly reactive metal. It is used in making light bulbs and for heat exchange in nuclear reactors.

Ions of elements

Combined together sodium and chlorine make common table salt and are thus essential to life. Table salt consists of sodium ions (Na+) and chloride ions (Cl-)

Steps for Naming Ions

1. Name polyatomic ions2. Name remaining anions (change ending to –

ide)3. Name remaining cations from groups 1, 2,

Ag+, Cd2+, Zn2+, Al3+. (use the name of the element and add “ion”)

4. Name all remaining cations using the name of the element followed by a roman numeral equal to the positive charge of the cation.

1. SO42-

2. O2-

3. Mg2+

4. Pb2+

5. NO2-

6. Ag+

7. Cu+

8. NH4+

9. P3-

10. Cl3+

Steps for Writing Formulas of Ions

• Many people find that they wish to do these in the order that they are presented. You can however use the following order if you find it helpful

1. Polyatomic ions.

2. Remaining anions. (These will be anything left that ends in –ide).

3. Remaining ions containing a Roman Numeral.

4. Remaining ions without a Roman Numeral. (get the roman numeral from the table).

1. Cobalt (I) ion

2. Selenide ion

3. Phosphite ion

4. Nitrogen (V) ion

5. Arsenide ion

6. Hydroxide ion

7. Cadmium ion

8. Lithium ion

9. Calcium ion

10. Mercury (I) ion

Homework

• Worksheet: Ions