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Ionic and Metallic Bonding. Chapter 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. - PowerPoint PPT Presentation
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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