Monday and Tuesday
March 26 and 27
Lewis Dot
Structures
Review?
1.What is a valence electron?
2.What is the lewis dot
structure of:
a) Lithium
b) Bromine
Do your
best to
answer on
your own.
Valence Electrons
The valence electrons are the electrons in the
last shell or energy level of an atom.
Why are they important?
-BONDING!
Valence Electrons
How many for each element?
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Lewis Dot Structures
What is the lewis dot structure
of:
a) Lithium
b) Bromine
Lewis Dot Structures
Draw
Draw the
the lewis
lewis dot
dot structure
structure
of
offor
calcium
oxygen
gas:
chloride:
methane
lithium
(CH
bromide:
4):
Identify the lone pairs
and bonding pairs!
**NO LONELY
ELECTRONS!!
Chemical Bonding
Types of Bonds,
Polarity, and Dipoles
What is electronegativity?
The ability of an element to steal
an electron from another
element
What are BONDS?
• The attraction between atoms
• Causes shape and structure of chemicals
Types of Bonds
• Non-polar (Covalent)
0.0
• Polar (Covalent)
0.1 to 1.9
• Ionic
2.0 or higher
Nonpolar Covalent Bond
Electronegativity Difference of 0.0
Electrons are shared equally
Polar Covalent Bond
Electronegativity Difference of 0.1 – 1.6
Electrons are shared, however, they favor one
side of the molecule.
Copyright © 2006 by the Regents of the University of California.
Copyright © 2006 by the Regents of the University of California.
Two types of Covalent Bonds
NONPOLAR
POLAR
Ionic Bond
Electronegativity Difference of 1.7 or higher
Electrons are transferred to the other element.
Types of Bonds
• Non-polar (Covalent)
0.0
• Polar (Covalent)
0.1 to 1.9
• Ionic
2.0 or higher
Practice
Draw the lewis dot structure for the formulas
below and identify the bond type:
Potassium Bromide
Carbon Disulfide
Nitrogen Trifluoride
Wednesday 3/28
and
Thursday 3/29
Modeling Lab
Friday 3/30
How are molecular shapes
determined?
VSEPR
Lewis Structures & VSEPR
Valence Shell Electron Pair Repulsion
electron pairs spread apart as far as possible
Electron Pair Geometry: Linear
Molecular Geometry: Linear
Number of Lone Pairs: 0
Number of Bonds: 2
Angle: 180̊
Electron Pair Geometry:
Trigonal Planar
Molecular Geometry:
Trigonal Planar
Number of Lone Pairs: 0
Number of Bonds: 3
Angle: 120̊
Electron Pair Geometry:
Trigonal Planar
Molecular Geometry: Bent
Number of Lone Pairs: 1
Number of Bonds: 2
Angle: 117̊
Electron Pair Geometry: Tetrahedral
Molecular Geometry: Tetrahedral
Number of Lone Pairs: 0
Number of Bonds: 4
Angle: 109.5̊
Number of Lone Pairs: 1
Number of Bonds: 3
Electron Pair Geometry: Tetrahedral
Molecular Geometry:
Trigonal Pyramidal
Angle: ~107̊
Electron Pair Geometry: Tetrahedral
Molecular Geometry: Bent
Number of Lone Pairs: 2
Number of Bonds: 2
Angle: 104.5̊
Questions on shape?
Dipoles
Contains a positive end and a negative end.
Copyright © 2006 by the Regents of the University of California.
Copyright © 2006 by the Regents of the University of California.
Copyright © 2006 by the Regents of the University of California.
Copyright © 2006 by the Regents of the University of California.
Practice
CO2
NH3
BF3
Li2O