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Chemistry 111

Sections 11.1 – 11.8 Chemistry 111

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Outline

• Recap of Chapter 10– Quantum Mechanics Rules– Valence Electrons & Noble Gas

Configuration

• Chapter 11.1 – 11.7:– Chemical Bonding with Ionic &

Covalent compounds.

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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

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Quantum Mechanics Steps

• Step #4: Electron Capacity, 2 e– per orbital

Sublevel # of Orbitals e- Capacity

s 1 12= 2

p 3 32= 6

d 5 52= 10

f 7 72= 14

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Quantum Mechanics Steps• Step #5: Energy level e– capacity.

n # Sublevels Names e– Capacity

1 1 s 12= 2

3 2 s, p 12= 2+32= 6 8

5 3 s, p, d 12= 2 32 = 6+52= 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

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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) = 1+ VIIA (7A) = 1-• IIA (2A) = 2+ VIA (6A) = 2-• IIIA (3A) = 3+ VA (5A) = 3-• IVA (4A) = ?

– 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 DiagramEach H counts 2 e- Fluorines each

count: LP 23=6 8 e- BP 21=2

Oxygens each count: LP 22=4 8 e- BP 22=4

NH3

H H F F

O ONH

H

H

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Big, Ugly Lewis Diagram

H gets 2 e-, C, N & O each get 8 e-

CC

CC

C

C

H

O

H

H

H

NH

H

H

O

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Exceptions

• Sometimes we can’t make everything work – and the octet rule gets broken.– Not enough Electrons

These “radicals” are quite reactive / Toxic

N O N OO

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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

H2.1

He

Li1.0

Be1.5

B2.0

C2.5

N3.0

O3.5

F4.0

Ne

Na0.9

Mg1.2

Al1.5

Si1.8

P2.1

S2.5

Cl3.0

Ar

K0.8

Ca1.0

Ga1.8

Ge1.8

As2.0

Se2.4

Br2.8

Xe

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Using Electronegativity (EN)

1. Look up the EN values for each Element:H = 2.1, F = 4.0

2. Compute the difference (make it >0)EN = 4.0 – 2.1 = 1.9

3. Rate the difference:< 0.4 Non-Polar0.4 – 0.9 Slightly Polar0.9 – 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…