Chapter 13: Electrons in the Atom

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Chapter 13Electrons in the Atom

• College Prep Chemistry

Orbital Interactive
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Evolution of Atomic Models

• 1. John Dalton
• indestructible mass
• - no subatomic particles

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Evolution of Atomic Models

• 2. J.J. Thomson plum-pudding model
• Discovered electrons
• electrons stuck into a lump of positively charged
  material
• mint chocolate chip ice cream model

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Evolution of Atomic Models

• 3. Ernest Rutherford
• nucleus of the atom is positively charged
• Evidence gold foil experiment

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Evolution of Atomic Models

• 4. Niels Bohr
• electrons travel in definite orbitals around the
  nucleus
• Energy level the region around the nucleus
  where the electron is likely to be moving
• Fixed energy levels analogous to the rungs of a
  ladder

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Evolution of Atomic Models

• Quantum Mechanical Model
• Describes the probability of finding an electron
  in a region of space around the nucleus
• It is impossible to know the exact position and
  momentum of an electron at the same time
• Based on probability rather than certainty
• Instead of traveling in defined orbits as Bohr
  proposed, electrons actually travel in diffuse
  clouds around the nucleus

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Principal Energy Levels (n)

• Principal (main) energy levels are assigned
  numbers according to their energy
• n1, 2, 3, 4
• Generally, energy increases with increasing n
• Distance of the electron from the nucleus
  increases with increasing n

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Sublevels

• For each principal energy level, there are one or
  more sublevels
• s, p, d, f
• of sublevels the principal energy level (n)
• For example,
• 1st principal energy level has 1 sublevel (s)
• 2nd principal energy level has 2 sublevel (s,p)
• 3rd principal energy level has 3 sublevels (s,p,d)

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Sublevels and Orbitals

• Each sublevel has a specific shape
• Each sublevel houses a specific of electron
  orbitals (where the electrons live)
• Each orbital can contain 2 electrons

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Sublevels and Orbitals

• s-sublevel
• Spherical in shape
• One orbital
• Contains 2e- maximum (2e- per each s orbital)

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Sublevels and Orbitals

• p-sublevel
• dumbbell in shape
• 3 orbitals
• Holds 6 e- maximum (2e- per each p orbital)

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Sublevels and Orbitals

• d-sublevel
• Double dumbbell in shape
• 5 orbitals
• Holds 10 e- maximum (2e- per each d orbital)

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Sublevels and Orbitals

• f-sublevel
• complex in shape
• 7 types of f-orbital
• Holds 14 e- maximum in each orbital (2e- per each
  f orbital)

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Atomic Orbital Chart
Energy Level of Sublevels  Sublevels  Sublevels  Sublevels  Sublevels Total of Electrons
    of Orbitals in each Sublevel of Orbitals in each Sublevel of Orbitals in each Sublevel of Orbitals in each Sublevel  
    1 3 5 7  




n1
1
s
2
p
2
s
8
n2
n3
d
3
p
18
s
n4
4
s
p
f
32
d
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Electron Arrangement in Atoms

• Electron Configuration the ways in which
  electrons are arranged around the nuclei of atoms
• Gives information about principal energy levels,
  sublevels, orbitals

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Three Rules determine electron configurations

1. The Aufbau Principal
2. Hunds Rule
3. Pauli Exclusion Principle

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Rules for Electron Configurations

• Aufbau principle
• Electrons enter orbitals of the lowest energy
  first
• The s sublevel is always the lowest in energy

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Rules for Electron Configurations

1. Aufbau principle Draw your own Aufbau filling
   diagram

7s 6s 5s 4s 3s 2s 1s (the
7 spelled out has an s)
7s 7p 6s 6p 5s 5p 4s 4p 3s 3p 2s 2p
(two peas in a pod) 1s
7s 7p 7d 6s 6p 6d 5s 5p 5d 4s 4p 4d 3s
3p 3d (we see in 3
dimensions!) 2s 2p 1s
7s 7p 7d 7f 6s 6p 6d 6f 5s 5p 5d 5f 4s
4p 4d 4f (the 4 spelled out has an f) 3s
3p 3d 2s 2p 1s
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Rules for Electron Configurations

1. Aufbau principle Draw your own Aufbau filling
   diagram

7s 7p 7d 7f 6s 6p 6d 6f 5s 5p 5d 5f 4s
4p 4d 4f 3s 3p 3d 2s 2p 1s

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Rules for Electron Configurations

• 2. Hunds Rule (hogs dont like each other)
• Every orbital in a sublevel is singly occupied
  before any orbital is doubly occupied
• All of the electrons in singly occupied orbitals
  have the same spin
• ? ? ?_

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Rules for Electron Configurations

• 3. Pauli Exclusion Principle
• an atomic orbital may have a maximum of two
  electrons
• Two electrons that occupy the same orbital must
  have opposite spins
• designated with ??

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Orbital Notation Examples

• Li ??
• 1s 2s
• B ?? ?? ?
• 1s 2s 2p
• C ?? ?? ? ?
• 1s 2s 2p

Hunds Rule
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Orbital Notation practice

• Elements 1-20
• Use the Aufbau Diagram Provided
• Remember all 3 rules!

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Electron Configurations

• A shorthand way of identifying the location of
  electrons

• C ?? ?? ? ?
• 1s 2s 2p
• C 1s2 2s2 2p2

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Electron Configurations
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Rearranging the e- configurations

• Scientists rearrange the configurations so that
  all similar energy levels stay together
• 21 Sc (fill with Aufbau first!)
• 1s22s22p63s23p64s23d1
• Then Switch!
• 1s22s22p63s23p63d14s2

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Noble Gas electron configurations

• Noble gas configurations look on the periodic
  table!
• 11 Na
• The noble gas that precedes Na is Ne 1s22s22p6
• So instead of 1s22s22p63s1 use Ne3s1

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Orbital blocks on the Periodic Table
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Exceptions to electron configurations

• 24 Cr
• 1s22s22p63s23p64s23d4
• ??
  ? ? ? ? __
• Takes less energy to half fill all orbitals
• 1s22s22p63s23p64s13d5
• ?_ ?
  ? ? ? ?_

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Exceptions to the electron configurations

• Also true for the rest of column 6 11
• 29 Cu
• Following the rules
• 1s22s22p63s23p64s23d9
• ??
  ?? ?? ?? ?? ?_
• Actual configuration
• 1s22s22p63s23p64s13d10
• ?_
  ?? ?? ?? ?? ??

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Section 13.3

• Physics and the Quantum Mechanical Model
• Electrons and Light

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Back to Bohr

• Bohrs model is based on atomic emission spectra
• Atoms only give off light of certain colors
  (wavelengths)

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Wave model of light

• Light is a wave with a frequency, speed and
  wavelength
• Emission of light is related to the behavior of
  electrons in an atom

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Parts of a Wave (1 of 2)

• Origin center line
• Wavelength (l) distance from crest to crest
• Amplitude (A) distance from origin to crest

amplitude
origin
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Parts of a Wave (2 of 2)

• Frequency (f) - of waves per second (s-1)
• SI Unit (Hertz)
• 1 Hz 1 s-1
• inversely related to wavelength

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Electromagnetic Radiation (EMR)

• a form of energy that exhibits wave-like behavior
  as it travels through space
• Includes radio waves, microwaves, infrared waves,
  Visible light, ultraviolet waves, X-rays and
  gamma rays
• All waves travel at the speed of light
• 3.0 X 108 m/s

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Visible Light

• A prism separates sunlight into a spectrum of
  colors
• Sunlight consists of a continuous range of colors
  
• Each color has a specific wavelength and f
• Red light lowest f, longest wavelength

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Electromagnetic Spectrum
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Wave model of light

• c l x f

Speed m/s
Wavelength m
Frequency Hz (hertz) 1/s
c Speed of light 3.00 x 108 m/s
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Calculating Frequency
Determine the frequency of light with a
wavelength of 500 nm?

• c l x f

l 500 nm 5 x 10-7 m
c 3.00 x 108 m/s
3.00 x 108 m/s (5 x 10-7 m) f
f 6.00 x 1014 Hz
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Calculating Wavelength

• What is the wavelength of the yellow light
  emitted by a sodium lamp if the frequency of the
  radiation is 5.10 x 1014 s-1?

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Sample Problem Answer

• Given f 5.10 x 1014 s-1
• c 3.00 x 108 m/s
• Unknown l
• Parent Equation c f x l
• Answer 5.88 x 10-7 m 588 nm

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Your turn 1

• What is the wavelength of radiation with a
  frequency of is 1.50 x 1013 s-1?

2.00 x 10 -5 m
Active Inspire
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Your turn 2

• What is the frequency of radiation with a
  wavelength of 5.00 x 10 -6 m?

6.00 x 10 13 s -1
Active Inspire
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Physics and the Quantum Mechanical Model

• Max Planck (1858-1947)
• Discovered a direct relationship between
  frequency and energy
• Higher frequency higher energy
• E h x f
• h Plancks Constant 6.63 x 10-34 Js

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Sample Problem

• What is the energy of a photon with a frequency
  of 5.00 x 1015 s-1?

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Sample Problem Answer

• Given f 5.00 x 1015 s-1
• h 6.63 x 10-34 J-s
• Unknown E ?
• Parent Equation E h x f
• Answer 3.32 x 10-18 J

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Your turn 1

• What is the energy of radiation with a frequency
  of is 5.50 x 1014 Hz?

Active Inspire
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Photoelectric Effect

• Photon - electron in the form of light
• Ground state normal position of electron
• Excited state electron jumps to higher energy
  level when energy is applied
• Photoelectric effect release of energy in the
  form of light when electron falls back to ground
  state
• Color of light emitted depends on the energy
  level of the electrons
• Blue light has a higher energy than red light

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Photoelectric Effect
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Atomic Emission Spectrum

• Elements emit light when electrocuted in gaseous
  form
• The light is passed through a prism and an atomic
  emission spectrum is obtained
• Atomic emission spectra are NOT continuous like
  sunlight
• Each line represents one distinct wavelength and
  frequency
• Every element has a unique emission spectra

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Atomic Emission Spectrum
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Spectrums

• When a narrow beam of emitted light is shined
  through a prism, it is separated into colors of
  the visible SPECTRUM

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Types of Spectrums

• Visible light Spectrum
• Continuous range
• Atomic emission spectrum
• Light emitted by an element through a prism
• Every element has a distinct emission spectrum
• Discontinuous
• Each line one frequency

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Different Elements Have Different Spectrums
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Video of Spectra via Spectroscopes

• http//www.mhhe.com/physsci/chemistry/essentialche
  mistry/flash/linesp16.swf
• http//www.flinnsci.com/atomicspectrum

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More practice problems with energy, frequency,
and wavelength

• Last page of your chapter 13 packet

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Chapter 13 Review Problems

• p. 386 22, 27, 28, 33, 34, 36, 38, 45, 47, 51,
  60, 63

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Evolution of Atomic Models

• 5. Quantum Mechanical Model (1 of 2)
• Quantum of energy amount of energy required to
  move an electron from one energy level to the
  next higher level
• Energy levels are not equally spaced
• Levels get closer together the further from the
  nucleus
• The further away from the nucleus, the less
  energy is required for an electron to escape

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