Chapter 5: Electrons In Atoms

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Chapter 5 Electrons In Atoms
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Wave Nature of Light

• Electromagnetic Radiation form of energy that
  exhibits wavelike behaviors as it travels through
  space
• Ex visible light, microwaves, x-rays, radio,
  etc.

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Wavelength

• Symbol ? (lambda)
• Defn distance between equivalent points on a
  curve

?
?
?
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Frequency

• Symbol f
• Defn number of waves that pass a given point
  in a second
• Unit Hertz (Hz)
• Ex 300 Hz 300 1/s 300 s-1

1/s
s-1
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Amplitude

• Defn waves height from origin to crest

crest
amplitude
origin
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Electromagnetic Waves

• All EM waves travels at the speed of light (c)
• c 3 x 108 m/s
• c (wavelength)(frequency)

c ?f
3 x 108 m/s
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Wavelength and Frequency Relationship

• Inversely related as one increases, other
  decreases

short ?
high frequency
long ?
low frequency
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Electromagnetic Spectrum

• Defn shows all forms of electromagnetic
  radiation

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Ex problem 1

• What is the wavelength of a microwave with a
  frequency of 3.44 x 109 s-1?

c ?f
c
3 x108 m/s
8.72 x 10-2 m

?

3.44 x 109 s-1
f
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Ex problem 2

• What is the frequency of green light, which has a
  wavelength of 4.90 x 10-7 m?

c ?f
c
3 x108 m/s


f
4.90 x 10-7 m
?
6.12 x 1014 Hz
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Particle Nature of Light

• Quantum minimum amount of energy that can be
  gained or lost by an atom
• Photoelectric Effect emission of electrons from
  metals surface when light of specific frequency
  shines on surface

light
e-
METAL
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• Photon particle of light
• Photon Energy
• Unit joules (J)
• formula

Ephoton hf
h Plancks constant 6.626 x 10-34 Js f
frequency (s-1)
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Ex problem

• What is the energy of a photon from the violet
  portion of the rainbow if it has a frequency of
  7.23 x 1014 s-1?

E hf
(6.626 x 10-34 Js)
(7.23 x 1014 s-1)
4.79 x 10-19 J
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Bohr Model of an Atom

• Ground State lowest energy state of an atom
• Excited State state when atom gains energy
• pay attention to the electrons
• Bohr Model shows electron orbit and energy
  level of an electron

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Bohr Model
E1 lowest energy level
E3 gt E2 gt E1
E1
E2
E3
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Ground State to Excited State
4
6

• in ground state, no energy radiated
• in excited state, electrons jump to higher
  energy level
• electron go from high E level to low E level
• photon emitted

1)
5
4
2)
3
3
2
Energy of atom
2
3)
1
4)
1
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Atomic Orbitals

• Defn 3D region around nucleus describing
  specific electrons location

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Principle Quantum Number (n)

• Defn indicates the energy level an electron is
  on
• - use periodic table to tell (look at rows)
• n 1,2,3,..

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Principal Quantum Number
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Energy Sublevels/Orbitals

• Defn shape of orbital that tells the path of
  the electrons
• 4 sublevels s, p, d, f
• Lets focus on the s and p orbitals

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s orbital

• Shape electrons travel in a sphere

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s orbital
3s
1s
2s
The greater the energy level, the bigger the
orbital
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p orbital

• Shape dumbbell or figure 8 shaped

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Electron Configuration

• Defn arrangement of electrons in an atom

Where are certain electrons located?
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Rules Governing Electron Configurations

• 1) Aufbau Principle electrons occupy lowest
  energy orbital available
• - fill up level 1 first, then level 2, etc.
• 2) Pauli Exclusion Principle there is a max
  number of electrons that occupy a single orbital
  (2)

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Rules Governing Electron Configurations

• 3) Hunds Rule if orbitals have equal energy,
  one e- will go in each orbital before doubling up

1
2
3
5
6
4
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Blocks On Periodic Table
s
s
p
d
f
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Divisions of Orbitals

• s orbital 1 sublevel (2 e- max)
• p orbital 3 sublevels (6 e- max)
• d orbital 5 sublevels (10 e- max)
• f orbital 7 sublevels (14 e- max)

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Orbital Diagram

• Nitrogen
• How many electrons?
• What energy level is nitrogen on?

7
n 2
1s
2s
2p
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Orbital Diagram

• Silicon
• How many electrons?
• What energy level is silicon on?

14
n 3
1s
2s
2p
3s
3p
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Orbital Diagram

• Copper
• How many electrons?
• What energy level is copper on?

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n 4
1s
2s
2p
3s
3p
4s
3d
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Electron Configuration Notation
2
2
4

• Oxygen (8 e-)
• Sulfur (16 e-)
• Vanadium (23 e-)
• Zirconium (40 e-)

2s
2p
1s
2
2
6
2
4
2s
2p
3s
3p
1s
2
2
6
2
6
2
3
2s
2p
3s
3p
4s
3d
1s
2
2
6
2
6
2
10
2
2
6
2s
2p
3s
3p
4s
3d
4p
5s
4d
1s
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Noble Gas Notation

• Rule start from previous noble gas, then
  write the configuration
• Oxygen
• Sulfur
• Vanadium
• Zirconium

2
4
He
2s
2p
2
4
Ne
3s
3p
2
3
Ar
4s
3d
2
2
Kr
5s
4d
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Valence Electrons

• defn electrons in outer most energy level
• - located in highest s p orbitals (max 8)
• N
• Mg
• Se

2
3
2
5 valence e-
2s
2p
1s
2
6
2
2
2 valence e-
2s
2p
1s
3s
2
6
2
6
2
2
10
4
2s
2p
1s
3p
4s
3s
3d
4p
6 valence e-
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Electron Dot Structure

• Defn shows number of valence e- by diagram
• Nitrogen (5 v.e.)
• Magnesium (2 v.e.)
• Selenium (6 v.e.)

N
Mg
Se