Chapter 5 “Electrons in Atoms” Pre-AP Chemistry Charles Page High School Stephen L. Cotton
Section 5.1 Models of the Atom <ul><li>OBJECTIVES: </li></ul><ul><ul><li>Identify  the inadequacies in the Rutherford atom...
Section 5.1 Models of the Atom <ul><li>OBJECTIVES: </li></ul><ul><ul><li>Identify  the new proposal in the Bohr model of t...
Section 5.1 Models of the Atom <ul><li>OBJECTIVES: </li></ul><ul><ul><li>Describe  the energies and positions of electrons...
Section 5.1 Models of the Atom <ul><li>OBJECTIVES: </li></ul><ul><ul><li>Describe  how the shapes of orbitals related to d...
Ernest Rutherford’s Model <ul><li>Discovered dense positive piece at the center of the atom-  “nucleus” </li></ul><ul><li>...
Niels Bohr’s Model <ul><li>Why don’t the electrons fall into the nucleus? </li></ul><ul><li>Move  like planets around the ...
The Bohr Model of the Atom Niels Bohr I pictured the electrons orbiting the nucleus much like planets orbiting the sun. Ho...
Bohr’s model <ul><li>Energy level  of an electron </li></ul><ul><ul><li>analogous to the rungs of a ladder </li></ul></ul>...
The Quantum Mechanical Model <ul><li>Energy is “quantized” - It comes in chunks. </li></ul><ul><li>A  quantum  is the amou...
Schrodinger’s Wave Equation Equation for the  probability  of a single electron being found along a single axis (x-axis) E...
<ul><li>Things that are very small  behave differently  from things big enough to see. </li></ul><ul><li>The  quantum mech...
<ul><li>Has energy levels for electrons. </li></ul><ul><li>Orbits are not circular. </li></ul><ul><li>It can only tell us ...
<ul><li>The atom is found inside a blurry “electron cloud” </li></ul><ul><li>An area where there is a  chance  of finding ...
Atomic Orbitals <ul><li>Principal Quantum Number  (n) = the energy level of the electron: 1, 2, 3, etc. </li></ul><ul><li>...
Principal Quantum Number Generally symbolized by “n”, it denotes the shell (energy level) in which the electron is located...
Summary s p d f # of shapes  (orbitals) Maximum electrons Starts at energy level 1 2 1 3 6 2 5 10 3 7 14 4
By Energy Level <ul><li>First Energy Level </li></ul><ul><li>Has only s orbital </li></ul><ul><li>only 2 electrons </li></...
By Energy Level <ul><li>Third energy level </li></ul><ul><li>Has s, p, and d orbitals </li></ul><ul><li>2 in s, 6 in p, an...
By Energy Level <ul><li>Any more than the fourth and not all the orbitals will fill up. </li></ul><ul><li>You simply run o...
Section 5.2 Electron Arrangement in Atoms <ul><li>OBJECTIVES: </li></ul><ul><ul><li>Describe  how to write the  electron c...
Section 5.2 Electron Arrangement in Atoms <ul><li>OBJECTIVES: </li></ul><ul><ul><li>Explain  why the actual electron confi...
aufbau diagram  - page 133 Aufbau is German for “building up” Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d ...
Electron Configurations… <ul><li>… are the way electrons are arranged in various orbitals around the nuclei of atoms.  Thr...
Pauli Exclusion Principle No two electrons in an atom can have the same four quantum numbers. Wolfgang Pauli To show the d...
Quantum Numbers Each electron in an atom has a unique set of  4 quantum numbers  which describe it. <ul><li>Principal quan...
Electron Configurations <ul><li>Hund’s Rule -  When electrons occupy orbitals of equal energy, they don’t pair up until th...
<ul><li>The first two electrons go into the 1s orbital </li></ul><ul><li>Notice the opposite direction of the spins </li><...
<ul><li>The next  electrons go into the 2s orbital </li></ul><ul><li>only 11 more... </li></ul>Increasing energy 1s 2s 3s ...
<ul><li>The next  electrons go into the 2p orbital </li></ul><ul><li>only 5 more... </li></ul>Increasing energy 1s 2s 3s 4...
<ul><li>The next  electrons go into the 3s orbital </li></ul><ul><li>only 3 more... </li></ul>Increasing energy 1s 2s 3s 4...
<ul><li>The last three electrons go into the 3p orbitals. </li></ul><ul><li>They each go into separate shapes (Hund’s) </l...
<ul><li>An internet program about electron configurations is: </li></ul><ul><li>Electron Configurations </li></ul><ul><li>...
Orbitals fill in an order  <ul><li>Lowest energy to higher energy. </li></ul><ul><li>Adding electrons can change the energ...
Write the electron configurations for these elements: <ul><li>Titanium - 22 electrons </li></ul><ul><ul><li>1s 2 2s 2 2p 6...
Chromium is actually: <ul><li>1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 3d 5 </li></ul><ul><li>Why? </li></ul><ul><li>This gives us tw...
Copper’s electron configuration <ul><li>Copper has 29 electrons so we expect:  1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 9 </li></u...
Irregular configurations of Cr and Cu Chromium steals a 4s electron to   make  its 3d sublevel  HALF FULL Copper steals a ...
Section 5.3 Physics and the Quantum Mechanical Model <ul><li>OBJECTIVES: </li></ul><ul><ul><li>Describe  the relationship ...
Section 5.3 Physics and the Quantum Mechanical Model <ul><li>OBJECTIVES: </li></ul><ul><ul><li>Identify  the source of ato...
Section 5.3 Physics and the Quantum Mechanical Model <ul><li>OBJECTIVES: </li></ul><ul><ul><li>Explain  how the frequencie...
Section 5.3 Physics and the Quantum Mechanical Model <ul><li>OBJECTIVES: </li></ul><ul><ul><li>Distinguish  between quantu...
Light <ul><li>The study of light led to the development of the quantum mechanical model. </li></ul><ul><li>Light is a kind...
- Page 139 “ R  O  Y  G  B  I  V” Frequency Increases Wavelength Longer
Parts of a wave Origin Wavelength Amplitude Crest Trough
Electromagnetic radiation propagates through space as a wave moving at the speed of light. Equation: c =  c = speed of l...
Wavelength and Frequency <ul><li>Are inversely related </li></ul><ul><ul><li>As one goes up the other goes down. </li></ul...
- Page 140 Use Equation:  c = 
Radiowaves Microwaves Infrared  .   Ultra-violet X-Rays GammaRays Long Wavelength Short Wavelength Visible Light Low Energ...
Wavelength Table Long  Wavelength = Low Frequency = Low ENERGY Short  Wavelength = High Frequency = High ENERGY
Atomic Spectra <ul><li>White light  is made up of all the colors of the visible spectrum. </li></ul><ul><li>Passing it thr...
If the light is not white <ul><li>By heating a gas with electricity we can get it to give off colors. </li></ul><ul><li>Pa...
Atomic Spectrum <ul><li>Each element gives off its own characteristic colors. </li></ul><ul><li>Can be used to identify th...
<ul><li>These are called the  atomic emission spectrum </li></ul><ul><li>Unique to each element, like fingerprints! </li><...
Light is a Particle? <ul><li>Energy is quantized. </li></ul><ul><li>Light is a form of energy. </li></ul><ul><li>Therefore...
The energy ( E  ) of electromagnetic radiation is  directly proportional  to the frequency (  ) of the radiation. Equatio...
The Math in Chapter 5 <ul><li>There are 2 equations: </li></ul><ul><li>c =   </li></ul><ul><li>E = h  </li></ul><ul><li...
Examples <ul><li>What is the wavelength of blue light with a frequency of 8.3 x 10 15  hz? </li></ul><ul><li>What is the f...
Explanation of atomic spectra <ul><li>When we write electron configurations, we are writing the lowest  energy. </li></ul>...
Changing the energy <ul><li>Let’s look at a hydrogen atom, with only  one electron , and in the first energy level. </li><...
<ul><li>Heat, electricity, or light can move the electron up to different energy levels.  The electron is now said to be  ...
<ul><li>As the electron falls back to the ground state, it gives the energy back as  light </li></ul>Changing the energy
Experiment #6, page 49-
<ul><li>They may fall down in specific steps </li></ul><ul><li>Each step has a different energy </li></ul>Changing the ene...
{ { {
<ul><li>The further they fall, more energy is released and the higher the frequency. </li></ul><ul><li>This is a simplifie...
What is light? <ul><li>Light is a  particle  - it comes in chunks. </li></ul><ul><li>Light is a  wave  - we can measure it...
Wave-Particle Duality J.J. Thomson won the Nobel prize for describing the electron as a  particle . His son, George Thomso...
Confused?  You’ve Got Company! “ No familiar conceptions can be woven around the electron; something  unknown  is doing  w...
The physics of the very small <ul><li>Quantum mechanics  explains how  very small  particles behave </li></ul><ul><ul><li>...
Heisenberg Uncertainty Principle <ul><li>It is impossible to know exactly the location and velocity of a particle. </li></...
Heisenberg Uncertainty Principle You can find out where the electron is, but not where it is going. OR… You can find out w...
It is more obvious with the very small objects <ul><li>To measure where a electron is, we use light. </li></ul><ul><li>But...
Moving Electron Photon Before Electron  velocity changes Photon wavelength changes After Fig. 5.16, p. 145
End of Chapter 5
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Chapter 5 electrons in atoms

  1. 1. Chapter 5 “Electrons in Atoms” Pre-AP Chemistry Charles Page High School Stephen L. Cotton
  2. 2. Section 5.1 Models of the Atom <ul><li>OBJECTIVES: </li></ul><ul><ul><li>Identify the inadequacies in the Rutherford atomic model. </li></ul></ul>
  3. 3. Section 5.1 Models of the Atom <ul><li>OBJECTIVES: </li></ul><ul><ul><li>Identify the new proposal in the Bohr model of the atom. </li></ul></ul>
  4. 4. Section 5.1 Models of the Atom <ul><li>OBJECTIVES: </li></ul><ul><ul><li>Describe the energies and positions of electrons according to the quantum mechanical model. </li></ul></ul>
  5. 5. Section 5.1 Models of the Atom <ul><li>OBJECTIVES: </li></ul><ul><ul><li>Describe how the shapes of orbitals related to different sublevels differ. </li></ul></ul>
  6. 6. Ernest Rutherford’s Model <ul><li>Discovered dense positive piece at the center of the atom- “nucleus” </li></ul><ul><li>Electrons would surround and move around it, like planets around the sun </li></ul><ul><li>Atom is mostly empty space </li></ul><ul><li>It did not explain the chemical properties of the elements – a better description of the electron behavior was needed </li></ul>
  7. 7. Niels Bohr’s Model <ul><li>Why don’t the electrons fall into the nucleus? </li></ul><ul><li>Move like planets around the sun. </li></ul><ul><ul><li>In specific circular paths, or orbits, at different levels. </li></ul></ul><ul><ul><li>An amount of fixed energy separates one level from another. </li></ul></ul>
  8. 8. The Bohr Model of the Atom Niels Bohr I pictured the electrons orbiting the nucleus much like planets orbiting the sun. However, electrons are found in specific circular paths around the nucleus, and can jump from one level to another .
  9. 9. Bohr’s model <ul><li>Energy level of an electron </li></ul><ul><ul><li>analogous to the rungs of a ladder </li></ul></ul><ul><li>The electron cannot exist between energy levels, just like you can’t stand between rungs on a ladder </li></ul><ul><li>A quantum of energy is the amount of energy required to move an electron from one energy level to another </li></ul>
  10. 10. The Quantum Mechanical Model <ul><li>Energy is “quantized” - It comes in chunks. </li></ul><ul><li>A quantum is the amount of energy needed to move from one energy level to another. </li></ul><ul><li>Since the energy of an atom is never “in between” there must be a quantum leap in energy. </li></ul><ul><li>In 1926, Erwin Schrodinger derived an equation that described the energy and position of the electrons in an atom </li></ul>
  11. 11. Schrodinger’s Wave Equation Equation for the probability of a single electron being found along a single axis (x-axis) Erwin Schrodinger Erwin Schrodinger
  12. 12. <ul><li>Things that are very small behave differently from things big enough to see. </li></ul><ul><li>The quantum mechanical model is a mathematical solution </li></ul><ul><li>It is not like anything you can see (like plum pudding!) </li></ul>The Quantum Mechanical Model
  13. 13. <ul><li>Has energy levels for electrons. </li></ul><ul><li>Orbits are not circular. </li></ul><ul><li>It can only tell us the probability of finding an electron a certain distance from the nucleus. </li></ul>The Quantum Mechanical Model
  14. 14. <ul><li>The atom is found inside a blurry “electron cloud” </li></ul><ul><li>An area where there is a chance of finding an electron. </li></ul><ul><li>Think of fan blades </li></ul>The Quantum Mechanical Model
  15. 15. Atomic Orbitals <ul><li>Principal Quantum Number (n) = the energy level of the electron: 1, 2, 3, etc. </li></ul><ul><li>Within each energy level, the complex math of Schrodinger’s equation describes several shapes. </li></ul><ul><li>These are called atomic orbitals (coined by scientists in 1932) - regions where there is a high probability of finding an electron. </li></ul><ul><li>Sublevels- like theater seats arranged in sections: letters s, p, d, and f </li></ul>
  16. 16. Principal Quantum Number Generally symbolized by “n”, it denotes the shell (energy level) in which the electron is located. Maximum number of electrons that can fit in an energy level is: 2n 2 How many e - in level 2? 3?
  17. 17. Summary s p d f # of shapes (orbitals) Maximum electrons Starts at energy level 1 2 1 3 6 2 5 10 3 7 14 4
  18. 18. By Energy Level <ul><li>First Energy Level </li></ul><ul><li>Has only s orbital </li></ul><ul><li>only 2 electrons </li></ul><ul><li>1s 2 </li></ul><ul><li>Second Energy Level </li></ul><ul><li>Has s and p orbitals available </li></ul><ul><li>2 in s, 6 in p </li></ul><ul><li>2s 2 2p 6 </li></ul><ul><li>8 total electrons </li></ul>
  19. 19. By Energy Level <ul><li>Third energy level </li></ul><ul><li>Has s, p, and d orbitals </li></ul><ul><li>2 in s, 6 in p, and 10 in d </li></ul><ul><li>3s 2 3p 6 3d 10 </li></ul><ul><li>18 total electrons </li></ul><ul><li>Fourth energy level </li></ul><ul><li>Has s, p, d, and f orbitals </li></ul><ul><li>2 in s, 6 in p, 10 in d, and 14 in f </li></ul><ul><li>4s 2 4p 6 4d 10 4f 14 </li></ul><ul><li>32 total electrons </li></ul>
  20. 20. By Energy Level <ul><li>Any more than the fourth and not all the orbitals will fill up. </li></ul><ul><li>You simply run out of electrons </li></ul><ul><li>The orbitals do not fill up in a neat order. </li></ul><ul><li>The energy levels overlap </li></ul><ul><li>Lowest energy fill first. </li></ul>
  21. 21. Section 5.2 Electron Arrangement in Atoms <ul><li>OBJECTIVES: </li></ul><ul><ul><li>Describe how to write the electron configuration for an atom. </li></ul></ul>
  22. 22. Section 5.2 Electron Arrangement in Atoms <ul><li>OBJECTIVES: </li></ul><ul><ul><li>Explain why the actual electron configurations for some elements differ from those predicted by the aufbau principle. </li></ul></ul>
  23. 23. aufbau diagram - page 133 Aufbau is German for “building up” Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f
  24. 24. Electron Configurations… <ul><li>… are the way electrons are arranged in various orbitals around the nuclei of atoms. Three rules tell us how: </li></ul><ul><li>Aufbau principle - electrons enter the lowest energy first. </li></ul><ul><ul><li>This causes difficulties because of the overlap of orbitals of different energies – follow the diagram! </li></ul></ul><ul><li>Pauli Exclusion Principle - at most 2 electrons per orbital - different spins </li></ul>
  25. 25. Pauli Exclusion Principle No two electrons in an atom can have the same four quantum numbers. Wolfgang Pauli To show the different direction of spin, a pair in the same orbital is written as:
  26. 26. Quantum Numbers Each electron in an atom has a unique set of 4 quantum numbers which describe it. <ul><li>Principal quantum number </li></ul><ul><li>Angular momentum quantum number </li></ul><ul><li>Magnetic quantum number </li></ul><ul><li>Spin quantum number </li></ul>
  27. 27. Electron Configurations <ul><li>Hund’s Rule - When electrons occupy orbitals of equal energy, they don’t pair up until they have to. </li></ul><ul><li>Let’s write the electron configuration for Phosphorus </li></ul><ul><ul><li>We need to account for all 15 electrons in phosphorus </li></ul></ul>
  28. 28. <ul><li>The first two electrons go into the 1s orbital </li></ul><ul><li>Notice the opposite direction of the spins </li></ul><ul><li>only 13 more to go... </li></ul>Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f
  29. 29. <ul><li>The next electrons go into the 2s orbital </li></ul><ul><li>only 11 more... </li></ul>Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f
  30. 30. <ul><li>The next electrons go into the 2p orbital </li></ul><ul><li>only 5 more... </li></ul>Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f
  31. 31. <ul><li>The next electrons go into the 3s orbital </li></ul><ul><li>only 3 more... </li></ul>Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f
  32. 32. <ul><li>The last three electrons go into the 3p orbitals. </li></ul><ul><li>They each go into separate shapes (Hund’s) </li></ul><ul><li>3 unpaired electrons </li></ul><ul><li>= 1s 2 2s 2 2p 6 3s 2 3p 3 </li></ul>Orbital notation Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f
  33. 33. <ul><li>An internet program about electron configurations is: </li></ul><ul><li>Electron Configurations </li></ul><ul><li>(Just click on the above link) </li></ul>
  34. 34. Orbitals fill in an order <ul><li>Lowest energy to higher energy. </li></ul><ul><li>Adding electrons can change the energy of the orbital. Full orbitals are the absolute best situation. </li></ul><ul><li>However, half filled orbitals have a lower energy, and are next best </li></ul><ul><ul><li>Makes them more stable. </li></ul></ul><ul><ul><li>Changes the filling order </li></ul></ul>
  35. 35. Write the electron configurations for these elements: <ul><li>Titanium - 22 electrons </li></ul><ul><ul><li>1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 2 </li></ul></ul><ul><li>Vanadium - 23 electrons </li></ul><ul><ul><li>1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 3 </li></ul></ul><ul><li>Chromium - 24 electrons </li></ul><ul><ul><li>1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 4 (expected) </li></ul></ul><ul><ul><li>But this is not what happens!! </li></ul></ul>
  36. 36. Chromium is actually: <ul><li>1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 3d 5 </li></ul><ul><li>Why? </li></ul><ul><li>This gives us two half filled orbitals (the others are all still full) </li></ul><ul><li>Half full is slightly lower in energy. </li></ul><ul><li>The same principal applies to copper. </li></ul>
  37. 37. Copper’s electron configuration <ul><li>Copper has 29 electrons so we expect: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 9 </li></ul><ul><li>But the actual configuration is: </li></ul><ul><li>1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 3d 10 </li></ul><ul><li>This change gives one more filled orbital and one that is half filled. </li></ul><ul><li>Remember these exceptions: d 4 , d 9 </li></ul>
  38. 38. Irregular configurations of Cr and Cu Chromium steals a 4s electron to make its 3d sublevel HALF FULL Copper steals a 4s electron to FILL its 3d sublevel
  39. 39. Section 5.3 Physics and the Quantum Mechanical Model <ul><li>OBJECTIVES: </li></ul><ul><ul><li>Describe the relationship between the wavelength and frequency of light. </li></ul></ul>
  40. 40. Section 5.3 Physics and the Quantum Mechanical Model <ul><li>OBJECTIVES: </li></ul><ul><ul><li>Identify the source of atomic emission spectra. </li></ul></ul>
  41. 41. Section 5.3 Physics and the Quantum Mechanical Model <ul><li>OBJECTIVES: </li></ul><ul><ul><li>Explain how the frequencies of emitted light are related to changes in electron energies. </li></ul></ul>
  42. 42. Section 5.3 Physics and the Quantum Mechanical Model <ul><li>OBJECTIVES: </li></ul><ul><ul><li>Distinguish between quantum mechanics and classical mechanics. </li></ul></ul>
  43. 43. Light <ul><li>The study of light led to the development of the quantum mechanical model. </li></ul><ul><li>Light is a kind of electromagnetic radiation. </li></ul><ul><li>Electromagnetic radiation includes many types: gamma rays, x-rays, radio waves… </li></ul><ul><li>Speed of light = 2.998 x 10 8 m/s, and is abbreviated “c” </li></ul><ul><li>All electromagnetic radiation travels at this same rate when measured in a vacuum </li></ul>
  44. 44. - Page 139 “ R O Y G B I V” Frequency Increases Wavelength Longer
  45. 45. Parts of a wave Origin Wavelength Amplitude Crest Trough
  46. 46. Electromagnetic radiation propagates through space as a wave moving at the speed of light. Equation: c =  c = speed of light, a constant (2.998 x 10 8 m/s)  (nu) = frequency, in units of hertz (hz or sec -1 )  (lambda) = wavelength, in meters
  47. 47. Wavelength and Frequency <ul><li>Are inversely related </li></ul><ul><ul><li>As one goes up the other goes down. </li></ul></ul><ul><li>Different frequencies of light are different colors of light. </li></ul><ul><li>There is a wide variety of frequencies </li></ul><ul><li>The whole range is called a spectrum </li></ul>
  48. 48. - Page 140 Use Equation: c = 
  49. 49. Radiowaves Microwaves Infrared . Ultra-violet X-Rays GammaRays Long Wavelength Short Wavelength Visible Light Low Energy High Energy Low Frequency High Frequency
  50. 50. Wavelength Table Long Wavelength = Low Frequency = Low ENERGY Short Wavelength = High Frequency = High ENERGY
  51. 51. Atomic Spectra <ul><li>White light is made up of all the colors of the visible spectrum. </li></ul><ul><li>Passing it through a prism separates it. </li></ul>
  52. 52. If the light is not white <ul><li>By heating a gas with electricity we can get it to give off colors. </li></ul><ul><li>Passing this light through a prism does something different. </li></ul>
  53. 53. Atomic Spectrum <ul><li>Each element gives off its own characteristic colors. </li></ul><ul><li>Can be used to identify the atom. </li></ul><ul><li>This is how we know what stars are made of. </li></ul>
  54. 54. <ul><li>These are called the atomic emission spectrum </li></ul><ul><li>Unique to each element, like fingerprints! </li></ul><ul><li>Very useful for identifying elements </li></ul>
  55. 55. Light is a Particle? <ul><li>Energy is quantized. </li></ul><ul><li>Light is a form of energy. </li></ul><ul><li>Therefore, light must be quantized </li></ul><ul><li>These smallest pieces of light are called photons . </li></ul><ul><li>Photoelectric effect? Albert Einstein </li></ul><ul><li>Energy & frequency: directly related. </li></ul>
  56. 56. The energy ( E ) of electromagnetic radiation is directly proportional to the frequency (  ) of the radiation. Equation: E = h  E = Energy, in units of Joules (kg·m 2 /s 2 ) (Joule is the metric unit of energy) h = Planck’s constant (6.626 x 10 -34 J·s)  = frequency, in units of hertz (hz, sec -1 )
  57. 57. The Math in Chapter 5 <ul><li>There are 2 equations: </li></ul><ul><li>c =  </li></ul><ul><li>E = h  </li></ul><ul><li>Know these! </li></ul>
  58. 58. Examples <ul><li>What is the wavelength of blue light with a frequency of 8.3 x 10 15 hz? </li></ul><ul><li>What is the frequency of red light with a wavelength of 4.2 x 10 -5 m? </li></ul><ul><li>What is the energy of a photon of each of the above? </li></ul>
  59. 59. Explanation of atomic spectra <ul><li>When we write electron configurations, we are writing the lowest energy. </li></ul><ul><li>The energy level, and where the electron starts from, is called it’s ground state - the lowest energy level. </li></ul>
  60. 60. Changing the energy <ul><li>Let’s look at a hydrogen atom, with only one electron , and in the first energy level. </li></ul>
  61. 61. <ul><li>Heat, electricity, or light can move the electron up to different energy levels. The electron is now said to be “ excited ” </li></ul>Changing the energy
  62. 62. <ul><li>As the electron falls back to the ground state, it gives the energy back as light </li></ul>Changing the energy
  63. 63. Experiment #6, page 49-
  64. 64. <ul><li>They may fall down in specific steps </li></ul><ul><li>Each step has a different energy </li></ul>Changing the energy
  65. 65. { { {
  66. 66. <ul><li>The further they fall, more energy is released and the higher the frequency. </li></ul><ul><li>This is a simplified explanation! </li></ul><ul><li>The orbitals also have different energies inside energy levels </li></ul><ul><li>All the electrons can move around. </li></ul>Ultraviolet Visible Infrared
  67. 67. What is light? <ul><li>Light is a particle - it comes in chunks. </li></ul><ul><li>Light is a wave - we can measure its wavelength and it behaves as a wave </li></ul><ul><li>If we combine E=mc 2 , c=  , E = 1/2 mv 2 and E = h   then we can get:  </li></ul><ul><ul><li> = h/mv (from Louis de Broglie) </li></ul></ul><ul><li>called de Broglie’s equation </li></ul><ul><li>Calculates the wavelength of a particle. </li></ul>
  68. 68. Wave-Particle Duality J.J. Thomson won the Nobel prize for describing the electron as a particle . His son, George Thomson won the Nobel prize for describing the wave-like nature of the electron. The electron is a particle! The electron is an energy wave!
  69. 69. Confused? You’ve Got Company! “ No familiar conceptions can be woven around the electron; something unknown is doing we don’t know what .” Physicist Sir Arthur Eddington The Nature of the Physical World 1934
  70. 70. The physics of the very small <ul><li>Quantum mechanics explains how very small particles behave </li></ul><ul><ul><li>Quantum mechanics is an explanation for subatomic particles and atoms as waves </li></ul></ul><ul><li>Classical mechanics describes the motions of bodies much larger than atoms </li></ul>
  71. 71. Heisenberg Uncertainty Principle <ul><li>It is impossible to know exactly the location and velocity of a particle. </li></ul><ul><li>The better we know one, the less we know the other. </li></ul><ul><li>Measuring changes the properties. </li></ul><ul><li>True in quantum mechanics, but not classical mechanics </li></ul>
  72. 72. Heisenberg Uncertainty Principle You can find out where the electron is, but not where it is going. OR… You can find out where the electron is going, but not where it is! “ One cannot simultaneously determine both the position and momentum of an electron.” Werner Heisenberg
  73. 73. It is more obvious with the very small objects <ul><li>To measure where a electron is, we use light. </li></ul><ul><li>But the light energy moves the electron </li></ul><ul><li>And hitting the electron changes the frequency of the light. </li></ul>
  74. 74. Moving Electron Photon Before Electron velocity changes Photon wavelength changes After Fig. 5.16, p. 145
  75. 75. End of Chapter 5

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