_____________ Bond
• Between nonmetallic elements of similar
electronegativity.
• Formed by sharing electron pairs
• Stable non-ionizing particles, they are not
conductors at any state
• FORM MOLECULES
• Examples; O2, CO2, C2H6, H2O, SiC
• Bonds in all the polyatomic ions and
diatomics are all covalent bonds
_____________ Chemical Bonds
• According to the Lewis model
– an atom may lose or gain enough electrons to
acquire a filled valence shell and become an ion.
An ionic bond is the result of the force of
attraction between a cation and an anion.
– an atom may share electrons with one or more
other atoms to acquire a filled valence shell. A
covalent bond is the result of the force of
attraction between two atoms with relatively
close electronegativities that share one or more
pairs of electrons.
____________ or _________ ???
• If the difference in electronegativities is
between:
– 1.7 to 4.0: Ionic
– 0.3 to 1.7: Polar Covalent
– 0.0 to 0.3: Non-Polar Covalent
Try KF, H2O, Cl2
Material from karentimberlake.com
and
H. Stephen Stoker
A. __________ of Bond Formation
• Potential Energy
– based on position of an object
– low PE =
high stability
C. Johannesson
A. Energy of Bond Formation
• Bond Energy
– Energy required to break a bond
Bond
Energy
Bond
Length
C. Johannesson
A. Energy of Bond Formation
• Bond Energy
– Short bond = ____________ bond energy
C. Johannesson
Drawing ________ Structures
1. Determine the number of valence electrons in the
molecule
2. Decide on the arrangement of atoms in the
molecule
3. Connect the atoms by single bonds
4. Show bonding electrons as a single line; show
nonbonding electrons as a pair of Lewis dots
5. In a single bond, atoms share one pair of electrons;
in a double bond, they share two pairs, and in a
triple bond they share three pairs.
Covalent Bonds
Two nonmetal atoms form a covalent
because they have less energy
after they
bonded
H +
H
H : H = HH = H2
hydrogen molecule
bond
B. Lewis Structures
• Electron Dot Diagrams
– show valence e- as dots
– distribute dots like arrows
in an orbital diagram
– 4 sides = 1 s-orbital, 3 p-orbitals
– EX: oxygen
C. Johannesson
X
B. Lewis Structures
• Octet Rule
– Most atoms form bonds in order to
obtain 8 valence e– Full energy level stability ~ Noble Gases
Ne
C. Johannesson
Double Covalent Bond
2 pairs of electrons are shared between 2 atoms
Example O2
Triple Covalent Bond
3 pairs of electrons are shared between 2 atoms
Example N2
Lewis Structures
Other molecules having single covalent bonds
H2O
The hydrogens share their electrons w/ oxygen
so that O has 8 e- and each H has 2 e-
Covalent Bonds in NH3
Learning Check
• Examples
– draw a Lewis structure for hydrogen peroxide, H2O2
– draw a Lewis structure for methanol, CH3OH
– draw a Lewis structure for acetic acid, CH3COOH
C. Molecular Nomenclature
• Prefix System (binary compounds)
1. Less e-neg atom
comes first.
2. Add prefixes to indicate # of atoms. Omit
mono- prefix on first element.
3. Change the ending of the
second element to -ide.
C. Johannesson
C. Molecular Nomenclature
PREFIX
monoditritetrapentahexaheptaoctanonadeca-
NUMBER
1
2
3
4
5
6
7
8
9
10
C. Johannesson
C. Molecular Nomenclature
CCl4
N2O
SF6
C. Johannesson
C. Molecular Nomenclature
arsenic trichloride
dinitrogen pentoxide
tetraphosphorus decoxide
C. Johannesson
__________ Elements
• Elements that are naturally in molecules with 2
atoms each.
• “H NO Halogens”
• Existing as diatomic molecule yields a stable octet
• Gases that exist as diatomic molecules are H2, F2,
N2, O2, Cl2, Br2, I2
• Examples Fluorine & Bromine
Material from karentimberlake.com
and
H. Stephen Stoker
Common Names:
Material from karentimberlake.com
and
H. Stephen Stoker
Learning Check
Fill in the blanks to complete the following names of
covalent compounds.
CO
carbon ______oxide
CO2
carbon _______________
PCl3
phosphorus _______chloride
CCl4
carbon ________chloride
N2O
_____nitrogen _____oxide
© Karen Timberlake
Learning Check
A. P2O5
B. Cl2O7
C. Cl2
Material from karentimberlake.com
and
H. Stephen Stoker
Bond Polarity: Polar
Polar covalent bond
 Electrons are shared between different
nonmetal atoms
 Due to differing electronegativities, some
elements will hold the e- more tightly than the
other in a covalent bond, therefore one side of
the molecule is partially (+) and one side of the
molecule is partially (-).
 Examples:
Cl2O
SO
Cl3N
Material from karentimberlake.com
and
H. Stephen Stoker
Chemical Bonding:
The Covalent Bond Model
← Fig. 5.12
(a) In the nonpolar covalent
bond present, there is a
symmetrical distribution of
electron density. (b) In the
polar covalent bond present,
electron density is displaced
because of its
electronegativity.
Material from karentimberlake.com
and
H. Stephen Stoker
B. Lewis Structures
• ____________ Covalent - no charges
• _________ Covalent - partial charges
+
+
C. Johannesson
Chemical Bonding:
The Covalent Bond Model
Fig. 5.13
(a) Methane is a nonpolar
tetrahedral molecule. (b)
Methyl chloride is a polar
tetrahedral molecule.
- water is a polar molecule because oxygen is more
electronegative than hydrogen, and therefore electrons
are pulled closer to oxygen.
B. Types of Bonds
IONIC
COVALENT
Bond
Formation
e- are transferred from
metal to nonmetal
e- are shared between
two nonmetals
Type of
Structure
crystal lattice
true molecules
Physical
State
solid
liquid or gas
Melting
Point
high
low
Solubility in
Water
yes
usually not
Electrical
Conductivity
yes
(solution or liquid)
no
Other
Properties
C. Johannesson
odorous