Chemistry 111
Sections 11.1 – 11.8
Chemistry 111
1
2
Outline
• Recap of Chapter 10
– Quantum Mechanics Rules
– Valence Electrons & Noble Gas
Configuration
• Chapter 11.1 – 11.7:
– Chemical Bonding with Ionic & Covalent
compounds.
3
Quantization – A Concept.
• Quantum means that a property (e.g.
electron’s energy, altitude in the classroom)
can only have certain values.
• Example:
–
–
–
–
–
going up stairs (is)/(is not) quantized
going up a ramp is (is)/(is not) quantized.
length of string is (is)/(is not) quantized
amount of flour in cookies (is)/(is not) quantized
number of eggs (is)/(is not) quantized
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Quantum Mechanics Steps
•
I have a 6-step program to review quantum
mechanics rules.
•
Step #1: Keep “n” from the Bohr Model
–
–
–
Quantum Mechanics refines Bohr’s Model
“n” is the “Principle Quantum Number”
Matches row number on the periodic table.
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Quantum Mechanics Steps
• Step #2: Add
“sublevels”
– s sublevels are spherical
– p sublevels are pear
shaped (2 flower petals)
– d sublevels are mostly
4-petal flowers
– f sublevels are mostly
8-petal flower
s
p
d
f
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Quantum Mechanics Steps
• Step #3: Add “orbitals”
Sublevel
# of Orbitals
s
1
p
3
d
5
f
7
7
Quantum Mechanics Steps
• Step #4: Electron Capacity, 2 e– per orbital
Sublevel
# of Orbitals
e- Capacity
s
1
12= 2
p
3
32= 6
d
5
52= 10
f
7
72= 14
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Quantum Mechanics Steps
• Step #5: Energy level e– capacity.
n
# Sublevels
Names
e– Capacity
1
1
s
12= 2
3
2
s, p
12= 2
+32= 6
8
5
3
s, p, d
12= 2
32 = 6
+52= 10
18
7
4
s, p, d f
… = 32
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Quantum Mechanics Steps
• Step #6: Orbital Filling / Building an Atom
– Recipe for an atom:
• Choose Element, add protons & neutrons
• Add electrons into orbitals until # e– = #p
– Filling Order:
• Start at lowest energy level
• Start at lowest suborbital
• Add electrons 1 at a time, remember to “use all empty
seats on the bus”
– Be capable of drawing the energy level diagram
– Write the electron configuration (1s22s22p63s2…)
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Valence Electrons
• Defined as electrons in outer shell
– We will mostly work with “s” & “p” electrons
• How many valence electrons in a neutral
atom?
– Column number on periodic table.
•
•
•
•
I A = 1 valence e–
II A = 2 valence e–
VI A = 6 valence e–
VIII A = 8 valence e–
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Noble Gas Electron Configuration
• Noble gases are special:
– They have full outer shells.
– Both s & p sublevels are full.
– They don’t want to react / bond with other atoms
• Everyone wants to be like a noble gas:
– Atoms form ions to get a full outer shell.
– Atoms share electrons to get a full outer shell.
• As we learned last time, the noble gas
electron configuration is: ns2np6
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Periodic Trends – Atomic Radii
13
Periodic Trends – Ionization Energy
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Chapter 11: Chemical Bonds
• Chapter 11 Topics
– Monatomic (1 atom)
Ions
– Ionic Bonds
– Covalent Bonds
– Covalent Bond
Polarity
– Multiple
(double/triple) Bonds
– Simple Molecules
– Metal Bonds
• What we’ll do:
– Discuss Ions
– Ionic Bond Movie
– Covalent Bonds
– Examples of Covalent
Bonds
– Polarity
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Ions
• We use the periodic table to predict what ions
an element forms.
• Noble Gas Configuration:
– Elements ionize to get a full or empty outer shell
(which ever is faster)
• Column Numbers
– Use the IA – VIIIA columns.
•
•
•
•
IA (1A)
IIA (2A)
IIIA (3A)
IVA (4A)
=
=
=
=
1+
2+
3+
?
VIIA (7A)
VIA (6A)
VA (5A)
=
=
=
123-
– Ignore Transition Metals for now.
• Examples: Na, Al, Se, As, Ba, Sb, I, Xe
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Movie
• Movie on ionization:
2 Na (s) + Cl2 (g)  2 NaCl (s)
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Covalent Bonds
• Recall from Previous Chemistry Class:
– Ionic = Electrons Transferred,
Covalent = Electrons shared.
– Lewis Diagrams Use:
• Elemental Symbols (1 for each atom in the molecule)
• Dots Represent Electrons (usually paired)
• Lines Represent Bonds (2 electrons per line)
– Things bond until they get 8 valence electrons
(except Hydrogen)
• Each atom take credit for all electrons in its bonds.
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Lewis Diagram
Each H counts 2 e-
Fluorines each count:
LP 23=6
BP 21=2
H
H
Oxygens each count:
LP 22=4
BP 22=4
O
8 e-
O
8 e-
F
F
NH3
H
H
N
H
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Big, Ugly Lewis Diagram
H
H
H
C
C
C
C
H
O
C
C
N
H
H
O
H
H gets 2 e-, C, N & O each get 8 e20
Exceptions
• Sometimes we can’t make everything
work – and the octet rule gets broken.
– Not enough Electrons
N
O
O
N
O
These “radicals” are quite reactive / Toxic
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Bond Polarity
• Covalent Bonds involve Sharing
Electrons but not all Sharing is equal!
• Hydrogen Fluoride is a good example.
– Fluorine is grabby and pulls electrons to it.
– Hydrogen isn’t as grabby and loses its
electrons
• We can use “Electronegativity” to
decide.
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Electronegativity Table
H
2.1
Li
1.0
Na
0.9
K
0.8
He
Be
1.5
Mg
1.2
Ca
1.0
B
2.0
Al
1.5
Ga
1.8
C
2.5
Si
1.8
Ge
1.8
N
3.0
P
2.1
As
2.0
O
3.5
S
2.5
Se
2.4
F
4.0
Cl
3.0
Br
2.8
Ne
Ar
Xe
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Using Electronegativity (EN)
1.
2.
3.
Look up the EN values for each Element:
H = 2.1, F = 4.0
Compute the difference (make it >0)
EN = 4.0 – 2.1 = 1.9
Rate the difference:
< 0.4
Non-Polar
0.4 – 0.9
Slightly Polar
0.9 – 1.7
Polar
> 1.7
Probably Ionic
Note: Hydrogen cannot form Ionic Bonds!
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Who cares about Polarity?
• Polar molecules (e.g. H2O) dissolve
other polar molecules.
• Polarity governs the TLC lab.
• Extreme Polarity holds DNA together.
• Polarity governs how proteins fold.
• Mayonnaise depends on polarity…
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