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
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