AlCl3
WHAT TYPE OF BOND
DO ALUMINUM AND
CHLORINE FORM?
AlCl3
WHAT TYPE Of BOND
DO ALUMINUM AND
CHLORINE FORM?
Ionic: Metal and NonMetal
AlCl3
WHAT TYPE Of BOND
DO ALUMINUM AND
CHLORINE FORM?
Ionic: Metal and NonMetal
COVALENT BOND
AlCl3
To muddy waters
even further, there
is no such thing as
a purely ionic or
covalent bond.
- -- - +11
A measure of an atom
or group of atom’s
tendency to attract
electrons
As you go down a group
Electronegativity
decreases.
Additional Electron shielding and increased
distance from the nucleus makes adding a
new electron more difficult
Increasing nuclear charge (pull) without any
additional shielding makes makes adding an
electron easier.
As you go across a period
Electronegativity increases.
Electronegativity (χ) is a “rule of thumb”
Bond type is ∝ to Δχ
Δ Electronegativity
ELECTRON TUG OF WAR!
Electron Tug of War
H-H Hydrogen 2.20
H-F Fluorine 3.98
Δχ
Bond Type
Example
0.0-0.5
Non-Polar Covalent
H2
≥0.5 to >1
Polar Covalent
HCl
≥1 to <2
Very Polar Covalent
HF
≥2
Ionic Bond
Na+Cl-
Electron Tug of War
NaCl
H2O
CO2
Electronegativity
Sliding Bond Scale
Water is a Polar Molecule!
H2O
Oxygen 3.44
Hydrogen 2.20
Drops on a Penny
Snapping Drops
Surface Tension
Sand vs Snowman
Capillary Action
Melting Points
Boiling Points
Solubility
Carbon Dioxide is Non-Polar
CO2
O C O
Oxygen 3.44
Carbon 2.55
Δχ=0.89
Why is Carbon
dioxide non-polar?
Carbon Dioxide is Non-Polar
δ-
δ+
δ-
O C O
Because it is linear or perfectly symmetrical.
CO2
Oxygen 3.44
Carbon 2.55
Δχ=0.89
Why is Carbon
dioxide non-polar?
Carbon Dioxide is Non-Polar
δ-
δ+
δ-
O C O
Because it is linear or perfectly symmetrical.
CO2
Oxygen 3.44
Carbon 2.55
Δχ=0.89
Why is Carbon
dioxide non-polar?
Water is Bent
δ-
H
δ+
O
H
δ+
Because water is not a linear molecule.
Why is Water Polar?
MOLECULAR GEOMETRY: VSEPR
δ-
H
δ+
O
H
δ+
Because water is not a linear molecule.
Why is Water Polar?
What about HCN?
δ+
δ-
H C N
CO2
Hydrogen 2.20
Carbon 2.55
Nitrogen
Prussic Acid is Polar
Because it is linear but the ends have opposite charges.
Two types of
Covalent Bonds
Non-Polar Covalent
• Electrons Shared Equally:
• --all diatomic molecules
Polar-Covalent
• Electrons Shared Unequally
• --due to electronegativity
δ Small Delta indicates
PARTIAL CHARGES
There is a small degree
of sharing and orbital
overlap even in ionic
bonds.
Practice Problems
What type of bond will
form between the
following atoms?
a)
b)
c)
d)
e)
f)
g)
h)
i)
j)
N and H
F and F
Ca and Cl
Al and Cl
H and Br
K and Cl
C and O
Cl and F
Li and O
H and O
Δ Electronegativity
Bond Type
0.0-0.5
Non-Polar Covalent
≥0.5 to >1
Polar Covalent
≥1 to <2
Very Polar Covalent
≥2
Ionic Bond (Extremely Polar)
Practice Problems
What type of bond will form
between the following atoms?
Place these covalent bonds in
order of least to most polar.
a)
b)
c)
d)
e)
f)
g)
h)
i)
j)
•
•
•
•
N (3) and H (2.1) = 0.9 mod PC
F (4) and F(4) = 0 = non-polar
Ca (1) and Cl (3) = 2 = Ionic
Al (1.5) and Cl (3) = 1.5 = very PC
H and Br mod PC
K and Cl ionic
C and O mod to very PC
Cl and F mod to very PC
Li and O ionic
H and O polar (thisH20!)
H—CL
H—Br
H—S
H—C
Answer: C and D tie to B to A