Modern Chemistry
Chapter 6
Chemical Bonding
Sections 1-5
Introduction to Chemical Bonding
Covalent Bonding & Molecular Compounds
Ionic Bonding & Ionic Compounds
Metallic Bonding
Molecular Geometry
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
1
Chapter Vocabulary
Molecule
Molecular compound
Chemical formula
Molecular formula
Bond energy
Electron-dot notation
Lewis Structure
Structural formula
Single bond
Multiple bond
Resonance
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
2
Section 2
Covalent Bonding
and
Molecular Compounds
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
3
Molecules
• A neutral group of atoms that are
held together by covalent bonds
• Has all the physical and chemical
properties of the compound
• May consist of two or more atoms of
the same element
Diatomic elements I2 Br2 Cl2 F2 O2 N2 H2
Molecular elements S8 P4
I Bring Clay For Our New House &
Swimming Pool.
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
4
Formulas
• Chemical Formula – indicates the
relative numbers of atoms of each
kind in a chemical compound by
using symbols and numeric
subscripts
• Molecular Formula – shows the
types and number of atoms in a
single molecule
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
5
Chemical Formula Animation
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
6
p. 179
Formation of Covalent Bonds
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
7
Formation of a Covalent Bond
• Forces to consider
– Electrons repel each other
– Protons and electrons attract each
other
– e- to p+ attraction is greater than the
e- to e- repulsion
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
8
Formation of a Covalent Bond
• Potential Energy and Stability
– High P.E. is related to low stability
– Low P.E. is related to high stability
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
9
p. 179
Bond Length & Stability
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
10
Characteristics of Covalent Bonds
• Bond Length – the distance between two
bonded atoms at their minimum potential
energy
• Energy is released when a bond forms
• The same amount of energy is required
to break that bond
• Bond Energy – the energy required to
break a chemical bond and form neutral
atoms.
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
11
p. 182
Bond Energy & Length Table
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
12
Bond Length Animation
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
13
Bond Energy Animation
p. xx
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
14
p. 183
Noble Gas Configuration
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
15
Octet Rule
• Chemical compounds tend to form so
that each atom by gaining, losing or
sharing electrons has an octet of
electrons in its highest energy level
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
16
Octet Rule Exceptions
• Less than 8 electrons
– Boron
• Three valence electrons
• Stable with only six instead of eight
– Beryllium
• Two valence electrons
• Stable with only four instead of eight
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
17
Octet Rule Exceptions
• Expanded valence - involves the d
orbitals as well as s & p
– Phosphorus
• Five valence electrons
• Stable with only ten instead of eight
– Sulfur
• Six valence electrons
• Stable with only twelve instead of
eight
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
18
Octet Rule Animation
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
19
Lewis Structures Animation
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
20
Lewis Structures
• Formulas in which the
symbols represent nuclei and inner shell
electrons,
dashes or dot-pairs between symbols
represent covalent bonds
and dots by one symbol represent
unshared pairs.
• Shared pairs = a bond
• Unshared pairs = a lone pear
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
21
Lone Pair Animation
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
22
Structural Formula
• Indicates the type, number and
arrangement of the atoms and the
bonds but not the unshared pairs
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
23
Structural Formula Animation
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
24
How to Draw Lewis Structures
1. Do the math to determine the
number of bonds
(1 x 8) + (3 x 2) + (1 x 8) = 22 e-
C H3 I
_
(1 x 4) + (3 x 1) + (1 x 7) = 14 e8 e- /2 = 4
All atoms
DivideAll
need
the
atoms
total
8 electrons
have
by 2 their
to to
getbethe
stable,
Subtract the “have”
from
the “need”.
Chapter 6 Section
2 Covalent
Bonding...
pages
178-189
valence
number
except
electrons
ofH bonds
which
available
in
only
the
needs
molecule.
for bonding.
2.
25
How to Draw Lewis Structures
2. Arrange the atoms as symetrically
as possible, with a central atom.
H
H C I
H
CHisand
thehalogens
centralChapter
atom
go
on
if2 Covalent
the
it is outside.
present.
6 Section
Bonding... pages 178-189
26
How to Draw Lewis Structures
3. Connect with bonds.
H
H C I
H
If you have too many bonds,
Chapter 6 Section 2 Covalent
pages 178-189
doubleBonding...
or triple
up.
27
How to Draw Lewis Structures
4. Add unshared pairs so that all
atoms have 8e- (except H)
H
H C I
H
A bond
Try page
counts
186
as
#1-4
two
Practice.
electrons.
Chapter
6 Section
2 Covalent
Bonding... pages 178-189
28
Multiple Covalent Bonds
Single bond: 2 e- are shared by 2 atoms
Double bond: 4 e- are shared by 4 atoms
Triple bond: 6 e- are shared by 3 atoms
Occur commonly with C, N and O
STRONG single bond SHORT
STRONGER double bond SHORTER
STRONGEST triple bond SHORTEST
Table on page 187
Try page 188 #1 & 2 Practice
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
29
Multiple Bonds Animation
p. xx
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
30
Resonance Structures
• Bonding in molecules that cannot be
correctly represented by a single
Lewis structure.
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
31
Resonance Animation
p. xx
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
32
Lewis Structures
Practice
• C2Cl4
• SCl2
• AsF5
• CI2Cl2
• BF3
• NO 1• CH2O
• IO3 1Chapter 6 Section 2 Covalent
Bonding... pages 178-189
33
Section 2 Homework
Chapter 6 Section 2 Worksheet
Chapter 6 Section 2 Covalent
Bonding... pages 178-189
34