CHEMICAL BONDING &
NAMING
Before we begin…
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Exceptions to the octet rule:
Atom
# of e- to be satisfied
Hydrogen (H)
2
Helium (He)
2
Lithium (Li)
2
Beryllium (Be)
4
Boron (B)
6
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YOU MUST MEMORIZE THESE!
Chemical Bonds
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The force that holds two atoms together is called a
chemical bond usually accompanied by a change
in energy.
Chemical bonds form because of attractions
between oppositely charged atoms, called ions, or
between electrons and nuclei.
Types of Chemical Bonds
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Valence electrons distribute themselves among ions
to form chemical bonds
 Ionic
bonds – the transfer of electrons due to an
electrical attraction between a cation and an anion
(usually a metal & a non-metal)
 Covalent Bond – the sharing of electrons between two
atoms (usually 2 or more non-metals)
 Metallic Bond – bonding between metals
How to determine type of bond
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The difference in electronegativity of the bonding
atoms can determine the type of bond that forms
0.0 < ∆EN < 0.5 non polar covalent
0.5 ≤ ∆EN < 1.9 polar covalent
∆EN ≥ 2.0 ionic
Percent Ionic Character
Polarity
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Non – polar covalent - covalent bond that equally
shares the electron (CO2)
Polar covalent the electron is not equally shared
(H2O)
The charge distribution is represented with a δ
(lower case delta)
Showing Polarity
+δ
+δ
H
H
O
H
H
O
-δ
Lewis Structures
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Helps determine the shape of the molecule
Dots represent electrons
Lines represent bonds (need two electrons to form a
bond)
Rules
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Calculate the maximum number of valence electrons
for each atom in the molecule (e- wanted)
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Remember exceptions (H, He, Li, Be, & B)
Calculate the actual number of valence electrons for
each atom in the molecule (e- have)
Subtract e- have from e- wanted = shared eDivide shared e- in half = bonds formed
Central atom is typically the atom in the center of the
molecule or the atom which is single & least
electronegative
F2
SO42-
More Practice