1. Chapter 4 Electron Configurations
4-1 Radiant energy
4-2 quantum theory
4-3 another look at the atom
4-4 a new approach to the atom
4-5 electron configurations

2. What do you see?

6. What do you see?
Having several different images w/in one is as confusing as the mystery of electrons were to the scientists.
There was no way to see them but they knew the electrons must be there
Scientists just didn’t know what to do about them or what they specifically did

7. 4-1 Radiant Energy
What are the 4 characteristics of an electromagnetic wave? What are the major regions of the electromagnetic spectrum?

8. Light
Most of what we know about how e- behave in atoms was learned from watching how light interacts w/ matter
Light travels through space and is a form of radiant nrg

9. Nature of Light The properties of light: Properties of wave
Properties of particles

10. Waves Light travels in waves like the ocean
These waves are electromagnetic wh. makes light a form of electromagnetic radiation
Electromagnetic radiation (x-rays, gamma rays, radio waves)
Electromagnetic waves have electric and magnetic fields oscillating at right angles to each other and to the direction of the motion of the wave

11. Waves All waves can be described by 4 characteristics Amplitude
Wavelength
Frequency
speed

12. Amplitude
The height of the wave
Determines the brightness/intensity

13. Wavelength Distance b/w wave crests
The distance it takes for the wave to make 1 cycle
Visible light has a wavelength b/w nanometers

14. Frequency Tells how fast the wave oscillates up and down
Measures how many cycles a wave makes in 1 second
Units: 1/s, s-1, 1 Hz
Radio stations broadcast at megahertz
97.5 FM means the frequency of those radio waves are moving at 97.5 x 106 cycles per second
Visible light moves b/w 4 x 1014 – 7 x 1014 s-1

15. Speed of light No matter the wavelength light moves at 3.00 x 108 m/s
b/c the speed does not change, relationships b/w wavelength and frequency can be made
The shorter the distance b/w the crests of a wave, the faster the wave oscillates up and down
The shorter the wavelength, the greater the frequency

16. λ = c/ν λ : wavelength c : speed of light – 3.00 x 108 ν : frequency
If given the frequency of 4.74 x 1014 s-1, what would the wavelength be?

17. Electromagnetic Spectrum

18. Types of waves: Infrared

19. Types of waves: x-rays

20. What is meant by nrg quantization?
4-2 Quantum Theory
What is meant by nrg quantization?
How is the nrg of radiation related to its wavelength? How does the idea of photons of light explain the photoelectric effect?

21. ???Unanswered questions???
Why would metal radiate different wavelengths at different temperatures?
Start heating, no visible light  Starts to glow red  White hot
Why do different elements have different colors?

22. Planck’s Theory Max Planck (1858-1947)
Proposed that there is a fundamental restriction on the amounts of nrg that an object emits/absorbs
Called these pieces of nrg quantum

23. Planck’s Theory Quantum/quanta Fixed amount
Goes against the previous theories of nrg

24. Planck’s Theory E = hν E = energy h = 6.626 x 10-34 J-s ν = frequency
Unit: joule-second
ν = frequency

25. Planck’s Theory
Using Planck’s theory, scientists can determine the temp of distant planets by measuring the λ of the electromagnetic radiation they emit

26. Planck’s Theory Energies absorbed/emitted by atoms are quantized
Means their values are restricted to certain quantities
What would happen if a car’s nrg was quantized?
A car can only go so fast

27. Planck’s Theory Look at figure 4-11 on pg 132
In which direction would a person walk on the ramp/stairs to increase her potential nrg?
Up the ramp/stairs
Is there any location on the ramp that can’t be occupied during this increase? No
How does a person’s movement on the stairs compare to a similar movement on the ramp?
To climb the stairs, a person can only occupy distinct levels/stairs
Would the motion of an elevator be continuous/not? Explain.
Yes, the motion is continuous, but people can only get off at certain levels.

28. Photoelectric Effect Albert Einstein (1879-1955)
When light of a certain frequency is shone on some metals, the electrons of that metal will be emitted from the surface
These emitted e- are filled with nrg and can be used thereafter
Solar calculators
Camera light meters
Each metal has a minimum frequency of light to release e-
Example: sodium metal is not affected by red light no matter its intensity. A very faint violet light however will cause the e- to be emitted

29. Photoelectric Effect Photons Particles of EM radiation No mass
Carry a quantum of nrg
nrg has certain minimum to cause ejection of photoelectron
Photon’s nrg must equal or exceed nrg needed to free an e- from an atom
nrg depends on frequency
Ephoton = hv

30. Photoelectric Effect Photon strikes surface of metal
Photon transfers nrg to e- in metal atom
e- chooses to “swallow” whole photon
If swallowed, e- will use nrg to “jump” off the atom
The important, deciding factor is the ν of the photon not the # of photons
So why does violet light release e- but not red?
Violet has a greater ν, therefore a greater amount of nrg/photon

31. Photoelectric Effect
nrg of a photon explains effects of different kinds of EM radiation
Hospitals have signs warning that x-rays are being used
X-rays have high ν which means high nrg photons wh. could cause harm to living organisms
Radio waves surround us w/o any warning signs
Low ν, low nrg photons wh. don‘t harm organisms.

32. Read the “Chemistry in Action” box on page 132
Photoelectric Cells
Read the “Chemistry in Action” box on page 132

33. 4-2 Section Review
p 134 (1-4)
What does it mean to say that nrg is quantized?
The nrg emitted/absorbed by any object is restricted to fixed amounts called quanta
How is the nrg of a quantum of radiant nrg related to its frequency?
The higher the frequency of light, the greater the nrg/photon
Why do you not ordinarily observe the quantization of nrg in the world around you?
Ea quantum of nrg is too small to notice in the everyday world
People who work around x-rays often wear film badges to monitor the amount of radiation to which they are exposed. Why do x-rays expose the film in the badge when other kinds of electromagnetic radiation do not?
X-rays have high frequencies. X-ray quanta have enough nrg to expose the film, whereas lower frequency waves do not.

34. Recap Video

35. Group Activity Each group will read their article
A PowerPoint will be made of the article information
The PowerPoint needs:
At least 5 slides
At least 2 pictures/diagrams
All members of the group presents

36. 4-3 Another Look at the Atom
What is a line spectrum? How does the Bohr model explain the line spectrum of hydrogen?

37. Line Spectra A spectrum that only contains certain colors/wavelengths
Also called the atomic emission spectrum
A fingerprint of that particular element
Ea. element has its own color
Sodium had a yellow color in your flame test

38. Atomic Emission Spectra
The set of frequencies of EM waves emitted by atoms of a particular element
Explains neon signs
Each element has a unique spectrum and therefore can be identified within an unknown such as through a flame test
Your lab last Monday

39. Atomic Emission Spectrum
Not every color of the spectrum seen in an emission spectrum b/c not all frequencies of light are emitted
Photo courtesy NASA Hydrogen spectrum
Photo courtesy NASA Helium spectrum

40. The painter is moving farther away from Earth’s surface
Why does it take more nrg for the painter to climb to the top rung of the ladder?
The electrons of an atom occupy orbitals around the atom’s nucleus that are similar to the rungs of a ladder.
The painter is moving farther away from Earth’s surface
climbing to the top rung.
For example, just as a person cannot step between the rungs of a ladder, an electron cannot occupy the space between the atom’s orbitals.
Why does the paintbrush hit the ground with more energy when it falls from the top rung?
Also, it takes energy for an electron to move from an orbital close to the atom’s nucleus to an orbital farther from the nucleus, just as it takes energy to move up the rungs of a ladder.
The paintbrush had more potential energy at the top of the ladder.

41. The Bohr Model of the Hydrogen Atom
Niels Bohr ( )
Attended lecture of Rutherford and used his, Planck, and Einstein’s theories
Focused on Hydrogen
Simplest w/ only 1 e-
Using Rutherford’s “planetary orbit” model of e- around the nucleus, Bohr said that ea. “orbit” specified a certain quantum of nrg

42. The Bohr Model of the Hydrogen Atom
Bohr labeled ea. nrg level (orbit) w/ a quantum #, n
The lowest nrg level (closest to nucleus), called ground state
n = 1
When the e- absorbs the right amount, it jumps to a higher nrg level
Called an excited state
Quantum #s: n=2, n=3, n=4, etc
Excited states represent larger orbits farther from the nucleus

43. The Bohr Model of the Hydrogen Atom

44. The Bohr Model of the Hydrogen Atom
Physics 2000

45. Matter Waves Movement of e-
We draw the orbitals as circles but the e- don’t actually move in a circle around the nucleus
e- move around as waves
Discovered by Louis de Broglie
1924
Physicist
French graduate student

46. Heisenberg’s Uncertainty Principle
If I put a balloon into a completely dark room, could you locate it without moving the balloon?
It is nearly impossible
Every time you touch the balloon it moves!
The e- is just like this

47. Heisenberg’s Uncertainty Principle Cont.
What if we put that same balloon in the dark room and gave you a flash light? Would you be able to find it now?
Yes, the tiny “photons” from the light reflect off the balloon & back into your eyes so that you see the balloon w/o having to touch it

48. Heisenberg’s Uncertainty Principle Cont.
When you hit the balloon w/ the photons, the balloon is so much bigger than the photons
When you hit an e- with a photon, the photon is the same size as the e- so they reflect off one another
After the “collision” the e- is now going in a different direction and is usually going much faster than before

49. Heisenberg’s Uncertainty Principle
States that there is no way to know exactly what an e- position and speed of an e- at any given time

50. Lasers
Read the Chemistry in Action on p 140

51. 4-3 Section Review
What is the difference b/w a line spectrum and a continuous spectrum?
Line spectrum contains only certain colors/wavelengths. Continuous spectrum contains all colors, wh. Fade gradually into ea. other
How does the Bohr model account for the line spectrum of the hydrogen atom?
The Bohr model labels the different nrg levels wh. Can be occupied by an e-. The e- absorbs/emits a certain quantity of nrg when it moves b/w these nrg levels. The frequencies in the line spectrum of hydrogen correspond to the quantity of nrg emitted when an e- moves from a higher to lower state.
What is Heisenberg’s Uncertainty Principle?
States the position and momentum of a moving object can’t simultaneously be measured and known exactly
You have learned that in attempting to locate an e-. The act of measurement changes the system. Suppose that you measure the temp. of a cup of hot tea with a cold thermometer. How does the use of the cold thermometer affect the temp reading? Is this an example of the uncertainty principle? Explain.

52. 4-4 A New Approach to the Atom
What is an atomic orbital? How do the s, p, d, and f orbitals compare in size, shape, and energy?

53. Quantum Mechanical Model
Model of the atom
Explains properties of the atom by treating electrons as waves that have quantized their energies
Though unable to tell exactly where an electron is or how it is moving
Model does describe probability that electrons will be found in certain locations around the nucleus

54. Probability and Orbitals
Electrons are seen in a blurry cloud or negative charge – electron cloud
More dense the area, the more probable to find electrons
Electron density: density of an electron cloud
High probability – high electron density
Low probability – low electron density

55. Probability and Orbitals
The probability of finding electrons in certain regions of an atom is described by orbitals
An atomic orbital is a region around the nucleus of an atom where an electron with a given energy is likely to be found
Orbitals have characteristic shapes, sizes, and energies

56. Probability and Orbitals
4 kinds of orbitals
s, p, d, and f
s orbital
Circle shaped
Increase in size w/ ea. increase in nrg level
p orbital
Dumbbell/figure eight shaped
d orbital
No definite shape
f orbital

57. Orbitals and Energy
Bohr suggested energies in electrons were quantized
These quantizations labeled as principle quantum levels designated by quantum #, n
Quantum Mechanical Model adds sublevels to these principle quantum levels
Sublevels have a pattern
# of sublevels equals the quantum #
n = 1 – 1 sublevel
n = 2 – 2 sublevels, etc

58. Orbitals and Energy

59. Orbitals and Energy Just like an address
You have a name, street, city, state, and zipcode
An electron has its principal energy level, the sublevel, and its orbital within that sublevel
First energy level
n = 1
One sublevel – s
Called the 1s sublevel and 1s orbital

60. Orbitals and Energy Second energy level n = 2 2 sublevels
2s – slightly larger than 1s
2p – consists of 3 orbitals
(px, py, pz)
x, y, & z stand for axis (3D)

61. Orbitals and Energy 3rd principle energy level n = 3 3 sublevels 3s 3p
3d – five orbitals

62. Orbitals and Energy 4th principal energy level n = 4 4 sublevels 4s 4p
4f – 7 orbitals

63. Electron Spin Electrons spin either clockwise or counterclockwise
Each orbit has 2 electrons
Each electron will have an opposite spin
Represented as arrows

64. 4-4 Review (p 146 1-4) What is an atomic orbital? An electron orbit?
Sketch the general shape of an s orbital and of a p orbital.
List the kinds of sublevels in the fourth principal energy level of an atom.
How many electron can be found in any orbital of an atom? Are their spins parallel or opposite?

65. Ground-State e- Configuration
Atoms want all their e- in a pattern and where they are supposed to be (organized)
When an atom has a lot of e-, they want them in the lowest nrg levels as possible

66. Aufbau Principle All sublevels of an nrg level have equal nrg
For example, in the 2p sublevel, the 2px, 2py, and 2pz orbitals are all equal in size
An f sublevel has more nrg than a d orbital, wh. has more nrg than a p, wh. has more nrg than an s
For example, a 2p is larger than a 2s

67. Aufbau Cont
It is possible for sublevels in one nrg level to overlap sublevels in another nrg level
For example, looking at nrg, a 4s orbital would be smaller than a 3d orbital
We would normally think they would go in order

68. Pauli Exclusion Principle
There are two e- in ea. orbital
ea. one has a different spin to it.
A 2s orbital would have 2 e- in it
A 2p orbital would have 2 e- in ea. of its orbitals (x, y, and z)
These different spins, mean one is spinning clockwise and the other counterclockwise.

69. Hund’s Rule
For ea. orbital in a sublevel (s, p, d, or f) will need special placement of the e-
There are 2 e- in ea. orbital, for however many orbital you have w/in a sublevel (1 for s, 3 for p, etc), you will need to place e- with the same spin in first and then add the others
Let’s look at some examples

70. Hund’s Rule 1. 2. 3. 4. 5. 6.

71. Orbital Diagrams A way to represent the e- in an atom
Lets you see the different spins in an orbital
What does it look like?
Empty box – empty orbital
Single up arrow – orbital w/ 1 e-
Up and down arrow – orbital w/ 2 e-

72. Orbital Diagrams Cont. Let’s look at Carbon
When we look at the periodic table, Carbon has an atomic # of 6
we know that means there are also 6 e-
Let’s put them in our boxes, but put them in order of orbitals 1s 2s 2p

73. Orbital Diagrams
With a partner, draw the orbital diagrams for Helium, Oxygen, and Fluorine

74. Electron Configuration Notation
Another way to represent the e- in an atom
Instead of drawing boxes, you make a list
For our Carbon example, we had 6 e- total
1s22s22p2
We have a chart we can use to let us know which orbitals to place in our list first

75. e- configurations
With your partner, write the e- configurations of Helium, Oxygen, and Fluorine.