Ionic and Metallic BondingChapter 7

Valence Electrons

• The electrons in the highest occupied

energy level

• Number of valence electrons is related to

the group number

Valence Electrons

Electron Dot Structures

• Diagrams that show valence electrons as

dots

The Octet Rule

• In forming compounds atoms tend to

achieve the electron configuration of a

noble gas

The Octet Rule

• Atoms of metals tend to lose electrons

• This leaves a full octet in the next lowest

energy level

• Atoms of nonmetals tend to gain electrons

or share

Formation of Cations

• If an atom loses an e- it becomes positively

charged

Formation of Anions

• If an atom gains an e- it becomes

negatively charged

Common Anions1- 2- 3-

F- fluoride O2- oxide N3- nitride

Cl- chloride S2- sulfide P3- phosphide

Br- bromide SO42- sulfate PO4

3- phosphate

I- iodide CO32- carbonate

OH- hydroxide

ClO- hypochlorite

NO3- nitrate

C2H3O2- acetate

HCO3- hydrogen

- carbonate

Assessment

• p 193 7.1 #1-10

Formation of Ionic Compounds

• Compounds composed of cations and

anions are called ionic compounds

Formation of Ionic Compounds

• Although they are composed of ions,

compounds are neutral

• The total positive charge of the cations

equals the total negative charge of the

anions

Ionic Bonds

• Anions and cations attract each other

• The electrostatic forces that hold ions

together are known as ionic bonds

Ionic Bonds

Ionic Bonds

Chemical Formula

• A chemical formula shows the kinds and

numbers of atoms in the smallest

representative unit of a substance

Formula Units

• The lowest whole number ratio of ions in

an ionic compound

1:1 ratio

Formula Unit

• A magnesium ion has a charge of +2

• A chloride ion has a charge of -1

•What is the formula unit?

Formula Unit

•Magnesium has a charge of +2

• Nitrogen has a charge of -3

•What is the formula unit?

7.2 Assessment

• p. 196 12-13

Properties of Ionic Compounds

•Most ionic bonds are crystalline structures

at room temperature

• Composition of crystals is very structured

Properties of Ionic Bonds

• Ionic Bonds generally have high melting

points

• Solutions of ions can conduct an electric

current

Electrode

Coordination Number

• The number of ions of opposite charge

that surrounds an ion in a crystal

Na+ - 6

Cl- - 6

Coordination Number

• Aluminum is +3

• Iodide is -1

•What is the formula unit?

Coordination Number

7.2 Assessment

• p 199 #14-22

Metallic Bonds

•Metals are made up of closely packed

cations rather than a neutral ion

•Metal atoms tend to share valence e-

• Sea of e-

Metallic Bonds

•Metallic bonds consist of the attraction of

the free-floating e- to the positively charge

metal ions

• These bonds hold metal together

• Ductile

• Maliable

Crystalline Structure of Metals

•Metal atoms are arranged in very compact

and orderly patterns

•Many different patterns are found

• p. 202

Alloys

•Most metals you encounter are alloys

• Alloys are mixtures composed of two or

more elements

Alloys

• Properties of alloys are usually superior to

properties of original elements

•What are some common alloys?

Alloys

• If atoms are similar in size they can replace

each other

• Substitutional alloy

Alloys

• If atoms are different sizes the smaller on

can fit into the spaces (interstices)

• Interstitial alloy

• Carbon fits between iron atoms forming

steel

7.3 Assessment

• p. 203 #23-27, 29

Chapter 7 Assessment

• pp. 207-208 #30-33, 35-37, 41-45, 48, 50