Download - Chapter 13: Phenomena
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Chapter 13: Bonding: General Concepts
Chapter 13: Phenomena
Phenomena: Scientists measured the bond angles of some common molecules.
In the pictures below each line represents a bond that contains 2 electrons. If
multiple lines are drawn together these are double or triple bonds and contain 4
and 6 electrons respectively. What patterns do you notice from the data?
H HN
H
H HN
H
H +
O
CO
O
CN H
Cl ClC
Cl
Cl
B
F
Bond Angles: 107˚
Bond Angles: 109.5˚ Bond Angles: 109.5˚
Bond Angles: 120˚
C
O
Bond Angles: 105˚
Bond Angles: 119˚
Bond Angles: 120˚ Bond Angle: 117˚
Bond Angles: 180˚
Bond Angles: 180˚
a) b) c)
d)
g)
e)
h)
f)
i)
j)
S
O
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Chapter 13
Bonding:
General Concepts
o Types of Bonding
o Electronegativity
o Lewis Structures
o Strength/Length of
Covalent Bonds
o Shapes of Molecules
(VSEPR)
o Polar Molecules
2
Big Idea: Bonds are formed
from the attraction
between oppositely
charged ions or by
sharing electrons.
Only the valence
electrons participate
in bonding. The shape
of the molecules
maximize the distance
between areas of high
electron density.
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Chapter 13: Bonding: General Concepts
Lewis Structure Review
Drawing Lewis Structures that Obey the Octet Rule
Step 3: Determine number of bonds
# 𝑏𝑜𝑛𝑑𝑠 =𝑤𝑎𝑛𝑡𝑒𝑑−𝑣𝑎𝑙𝑒𝑛𝑐𝑒
2
Step 4: Determine number of electrons
# 𝑒− = 𝑣𝑎𝑙𝑒𝑛𝑐𝑒 − 2 𝑏𝑜𝑛𝑑𝑠
3
CO32- 1(C) 3(O) 2(e-) Total
Step 1:
(Determine
Valence e-)
Step 2:
(Determine
Wanted e-)
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Chapter 13: Bonding: General Concepts
Lewis Structure Review
Resonance: A blend of Lewis structures into a
single composite hybrid structure.
Formal Charge = Valence e- – e- Surrounding Atom
4
O
O
O C
2-O
OO C O
O
OC
2- 2-
Note: Loan pairs count for 2 e- and bonds count for 1 e-.
O
O
O C
2-
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Chapter 13: Bonding: General Concepts
Lewis Structure Review
Drawing Lewis Structures that Minimize Formal Charges (Only atoms in period 3 and later can
expand their octets)
Step 2: Find structure with lowest formal charges
5
SO2 1(S) 2(O) Total
Step 1:
(Determine
Valence e-)
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Chapter 13: Bonding: General Concepts
Shapes of Molecules (VSEPR)
VSEPR (Valence-Shell Electron-Pair Repulsion Model):
Extends Lewis’s theory of bonding to account for
molecular shapes by adding rules that account for
bond angle.
Rule 1: Regions of high electron concentration
(bonds and lone pairs on the central atom) repel
one another and to minimize their repulsion,
these regions move as far apart as possible while
maintaining the same distance from the central
atom.
Rule 2: There is no distinction between single and
multiple bonds: a multiple bond is treated as a
single region of high electron concentration.
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Chapter 13: Bonding: General Concepts
Shapes of Molecules (VSEPR)
Rule 3: All regions of high electron density, lone
pairs and bonds, are included in a description of
the electronic arrangement, but only the
positions of atoms are considered when
reporting the shape of a molecule (molecular
shape).
Rule 4: The strengths of repulsion are in the order
lone pair – lone pair > lone pair – atom > atom –
atom.
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Chapter 13: Bonding: General Concepts
Shapes of Molecules (VSEPR)
Assigning Shape and Bond Angles of Molecules
Step 1: Draw the Lewis structure.
Step 2: Assign the electronic arrangement
around the central atom (linear, trigonal planer,
tetrahedral)
Step 3: Identify the molecular shape (linear,
bent, trigonal planer, trigonal pyramidal,
tetrahedral)
Step 4: Figure out the bond angle (allow for
distortion)
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Note: Electronic arrangement includes all areas of electron density
(lone pairs and bonds).
Note: Molecular shape includes only bonds.
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Chapter 13: Bonding: General Concepts
Shapes of Molecules (VSEPR)
Possible Electronic Arrangements
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Chapter 13: Bonding: General Concepts
Shapes of Molecules (VSEPR)
Possible Molecular Arrangements
The names of the shapes of simple molecules and their bond angles. Lone pairs of electrons are not shown.
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Chapter 13: Bonding: General Concepts
Shapes of Molecules (VSEPR)
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No Lone PairsTetrahedral
1 Lone PairTrigonal Pyramidal
2 Lone PairsBent
No Lone PairsTrigonal Planar
1 Lone PairBent
No Lone PairsLinear
3 Areas of
Electron
Density
2 Areas of
Electron
Density
4 Areas
of
Electron
Density
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Chapter 13: Bonding: General Concepts
Shapes of Molecules (VSEPR)
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No Lone Pairs
Trigonal
Bipyramidal
2 Lone
Pairs
T-Shaped
3 Lone
Pair
Linear
1 Lone
Pair
Seesaw
5 Areas of
Electron Density
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Chapter 13: Bonding: General Concepts
Shapes of Molecules (VSEPR)
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No Lone
Pairs
Octahedral
1 Lone Pair
Square
Pyramidal
3 Lone
Pairs
T-Shaped
4 Lone Pair
Linear
2 Lone Pairs
Square Planer
6 Areas of Electron
Density
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Chapter 13: Bonding: General Concepts
Shapes of Molecules (VSEPR)
Step 1: Draw Lewis Structure
Determine number of bonds
# 𝑏𝑜𝑛𝑑𝑠 =𝑤𝑎𝑛𝑡𝑒𝑑−𝑣𝑎𝑙𝑒𝑛𝑐𝑒
2
Determine number of electrons
# 𝑒− = 𝑣𝑎𝑙𝑒𝑛𝑐𝑒 − 2 𝑏𝑜𝑛𝑑𝑠
Step 2: Determine Electronic Shape
Step 3: Determine Molecular Shape
Step 4: Determine Angle
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CH4 1(C) 4(H) Total
Valence e-
Wanted e-
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Chapter 13: Bonding: General Concepts
Shapes of Molecules (VSEPR)
Step 1: Draw Lewis Structure (Obeys Octet Rule)
Determine number of bonds
# 𝑏𝑜𝑛𝑑𝑠 =𝑤𝑎𝑛𝑡𝑒𝑑−𝑣𝑎𝑙𝑒𝑛𝑐𝑒
2
Determine number of electrons
# 𝑒− = 𝑣𝑎𝑙𝑒𝑛𝑐𝑒 − 2 𝑏𝑜𝑛𝑑𝑠
Step 2: Determine Electronic Shape
Step 3: Determine Molecular Shape
Step 4: Determine Angle
15
SO32- 1(S) 3(O) 2(e-) Total
Valence e-
Wanted e-
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Chapter 13: Bonding: General Concepts
Student Question
Shapes of Molecules (VSEPR)
What is the most likely shape of ICl4-?
Helpful Hint: Make sure that your formal
charges are minimized.
a) Octahedral
b) Trigonal Planar
c) Seesaw
d) Tetrahedral
e) None of the Above
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Chapter 13: Bonding: General Concepts
Student Question
Polar Molecules
Is PCl4- polar or nonpolar?
Helpful Hint: Make sure that your formal
charges are minimized.
a) Polar
b) Nonpolar
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Chapter 13: Bonding: General Concepts
Take Away From Chapter 13
Big Idea: Bonds are formed from the attraction
between oppositely charged ions or by sharing
electrons. Only the valence electrons participate in
bonding. The shape of the molecules maximize the
distance between areas of high electron density.
Lewis Structures
Be able to draw Lewis structures of covalent
compounds. (57,58)
Know how to calculate formal charges.(78,79)
Identification of most likely Lewis structure.
Know when multiple resonance structures are possible for a
compound.(60,61,65,73)
Know when atoms can expand their octets (group 3 and
greater).(80)
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Numbers correspond to end of chapter questions.
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Chapter 13: Bonding: General Concepts
Take Away From Chapter 13
Shape of Molecules (VSEPR) (88,91)
Know how to determine electronic shape.
Linear, trigonal planar, tetrahedral, trigonal bipyramidal, or
octahedral.
Know how to determine molecular shape.
Linear, angular, trigonal planar, trigonal pyramidal, T-
shaped, tetrahedral, seesaw, square planar, trigonal
bipyramidal, square pyramidal, or octahedral.
Know how to determine bond angles.
Polar Molecules
Be able to determine if a molecule is polar or non polar.
(93,94)
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Numbers correspond to end of chapter questions.