Three Types Of Bonding Chemical Bonding Sheet Page 2
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1
2Lewis symbols conisist of the atomic symbol surrounded by
valnece electrons. The four sides represent the four valence
orbitals. Atoms are usually shown in their excited states (II,
III, IV)
15 • Chemical Bonding
Li
Be
B C
N
O
F
Ne
Lewis Electron Dot Structures
(5 of 8)
Ions include brackets. Positive ions show no valence
electrons while negative ions usually have an octet.
+
2+
2–
[Li]
[Mg]
[ O ]
Compound
Molecular
Ionic
Conducts as Solid
NO
NO
Conducts as Liquid
NO
YES
Conducts in Solution
NO
YES
Conducts as Gas
NO
YES
15 • Chemical Bonding
Comparing Ionic and Molecular Substances
Hardness
soft
hard
(6 of 8)
MP / BP
low
high
Bonding
covalent
ionic
Examples
He, CH
, CO
,
NaCl, KI,
4
2
C
H
O
AgNO
6
12
6
3
You will be given a chart of electronegativity values.
Memorize the most electronegative element s (F = 4.0)
then oxygen (O = 3.5) and chlorine (Cl = 3.0). The noble
gases have no electronegativity values… no bonds.
Trend is large electronegativity in the upper right of the
15 • Chemical Bonding
per. table and small in the lower left portion of the table.
Electronegativity and Polar Bonds
Classify the bond between any two atoms by subtracting
(7 of 8)
their electronegativity values (∆e)
0 < ∆e < 0.5
Non-polar covalent
0.5 ≤ ∆e ≤ 1.7
Polar covalent
∆e > 1.7
Ionic
The more electronegative atom is more negative.
Polar covalent bonds have partial charges δ+ and δ–
Use VSEPR theory to predict the shape of molecules. The
Steric Number (the number of lone pairs + bonded
atoms) corresponds to the shape of the electron pairs
around a central atom.
[1=linear, 2=linear, 3=trigonal planar, 4=tetrahedral]
15 • Chemical Bonding
Shapes and Polar Molecules
If each shape is symmetrical, the bond dipoles will cancel
(8 of 8)
resulting in a nonpolar molecule.
If a shape has lone pairs of electrons on the central atom,
the shape is often unsymmetrical, the molecule is polar.
Polar molecules and ions dissolve well in polar solvents
while nonpolar molecules dissolve in nonpolar solvents.
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