Unit 5: Chemical Bonding
Introduction to Bonding
(p. 161 – 163)
Chemical bond:
 attractive force between the valence
electrons of different atoms that binds them
together
 Occurs when atoms are unstable
Why do bonds form?
 To become more stable (decrease
potential energy)
Octet Rule:
 when atoms obtain 8 valence electrons on
it’s outer-most energy level
 Atoms will gain, lose, or share electrons
until it has 8 valence e- (become stable)
H
O
3 Types of Chemical Bonds
1.
2.
3.
Ionic Bond: when atoms gain or
lose electrons
Covalent Bond: when atoms share
electrons (polar or nonpolar)
Metallic Bond: attraction b/t metal
atoms and surrounding sea of
electrons
Quick Review
Metals?
Nonmetals?
Metalloids?
Types of Chemical Bonds
IONIC
BONDS
COVALENT
BONDS
POLARCOVALENT
BONDS
METALLIC
BONDS
NON-POLAR
COVALENT
BONDS
IONIC BONDS
Bond
Formation
Type of Structure
e- are transferred from
Metal to Nonmetal
crystal lattice
Physical State
solid
Melting Point
High *
Solubility in Water
Electrical
Conductivity
Other Properties
yes
yes
(solution or liquid)
Ionic Bonds- crystal lattice
+
Na
Cl
1 valence 7 valence
ee-
NaCl
COVALENT BONDS
Bond
Formation
Type of Structure
Physical State
Melting Point
Solubility in Water
Electrical
Conductivity
Other Properties
e- are shared between
2 Nonmetals
true molecules
liquid or gas
low
usually not
no
odorous
Covalent Bonds – atoms share
electrons
Covalent Bonds - molecules
Diatomic
Molecule2 identical atoms
NH3
Cl2
H2O
METALLIC
Bond
Formation
Type of Structure
Physical State
Melting Point
Solubility in Water
Electrical
Conductivity
Other Properties
e- are delocalized
among metal atoms
“electron sea”
solid
very high
no
yes (any form)
malleable, ductile,
lustrous
Metallic Bonds
Metallic
Bonding “Electron
Sea”
Ionic or Covalent?
NaCl
H2 O
LiBr
CaCl2
NH3
CO2
KI
NO3








Ionic (m+ nm)
Covalent (nm +nm)
Ionic
Ionic
Covalent
Covalent
Ionic
Covalent
Bond Polarity
Polar:
Nonpolar:
Uneven distribution
of a charge
Even distribution of a
charge
Polar Covalent Bond
 e- are shared unequally
 asymmetrical e- density
 usually different atoms: HCl
 results in partial charges ( partial + and
partial-)
+

( = delta)

Nonpolar Covalent Bond
 e are shared equally
 symmetrical e density
 usually identical atoms:
Cl2
Classify as Ionic, Polar, or Nonpolar :
Nonpolar
O2
Polar
HBr
Ionic
KF
Electronegativity: The attraction an
atom has for a shared pair of electrons.
Increases up and to the right.
Electronegativity
In a compound, the higher EN atom,
the more negative it will be  In a compound, the lower EN atom,
+
the more positive it will be  
H = 2.1
Cl = 3.0
Bond types can be determined by
calculating the difference in
electronegativity (EN) (Most bonds are a
blend of ionic & covalent)
H = 2.1
Cl = 3.0
Ionic:
1.7  3.3
PolarCovalent:
0.3  1.7
NonpolarCovalent:
0  0.3
What type of bond is formed between
Hydrogen and Chlorine?
0.9
3.0 – 2.1 = ______
Polar-Covalent Bond
Bond Type: __________________
H = 2.1
Cl = 3.0
Examples:
Cl2
NH3
3.0 - 3.0 = 0.0
Nonpolar
3.0 - 2.1 = 0.9
Polar
NaCl 3.0 - 0.9 = 2.1
Ionic