1. Electrons in the Atom
Chapter 5

2. Rutherford to Bohr
Rutherford’s model had the correct particles of the atom
But could not explain the properties of elements.
Niels Bohr proposed that electrons moved in circular orbits around the nucleus.
Each orbit distance has a certain amount of energy.
“Energy levels”

3. A Reminder: Potential Energy
Potential energy is the energy of position.
Energy can be stored by raising a mass.
PE = (mass)x(gravity)x(height)
It takes energy to go up
Energy is released when things go down

4. The Bohr Model Electrons move in Energy Level “orbits”
Like the rungs of a ladder
You can go up
Takes energy to do it
You can go down
Energy is lost
Bohr noticed that it was only certain amounts of energy could be released
“Quantums” of certain quantities of energy.

7. Bohr solves one problem, has his own
Bohr’s model perfectly predicts the behavior of the hydrogen atom
The simplest atom, with only one electron
But not any others!
Schrödinger gives up on the idea of the electron as a particle, and says “It’s a wave of probability!”
LOL
PWND, Bohr!

8.
11:15 then Go to Vegas

9. The Quantum Mechanical Model
Schrödinger describes electrons as a wave
Shows electrons do have certain quantities, you just don’t know exactly where the electrons are.
You can determine where the electrons PROBABLY are (in a certain volume) but can’t be 100% sure.
Creates “orbitals” of probability where electrons probably are.

10. The World’s Weirdest Hotel
4 floors
Not well designed.

11. Atomic Orbitals Electrons are found in orbitals of probability
These orbitals each have an energy level (like Bohr said) with different amounts of energy
Each energy level has sub-levels of energy
Level 1 = 1 sublevel
Level 2 = 2 sublevels
Level 3 = 3 sublevels
Level 4 = 4 sublevels

12. The 4 energy levels. Level 1 (n=1) – s sub-level
Level 2 (n=2) – s and p sub-levels
Level 3 (n=3) – s, p, and d sub-levels
Level 4 (n=4) – s, p, d, and f sub-levels
s, p, d, and f are sets of shapes (orbitals)
s = 1 orbitals (sphere)
p = 3 orbitals (x, y, and z buns)
d = 5 orbitals
f = 7 orbitals

13. Where the electrons go.
The way the electrons are arranged is the electron configuration
Configurations follow three rules:
Aufbau principle
The Pauli exclusion principle
Hund’s rule

14. Aufbau Principle “Electrons are lazy”
Electrons will automatically go to the lowest energy sub-level available 1s
then 2s
then 2p
then 3s
then 3p
then 4s
then 3d
then 4p

15. Pauli Exclusion Principle
“Electrons don’t like similar electrons.”
Electrons have two spins (up and down or clockwise and counterclockwise)
Only two electrons may fit in each orbital
One can spin each direction, and you can’t fit two electrons spinning the same ways.
Ex) 1s has 1 orbital, so it can fit 2 electrons
Ex) 2p has 3 orbitals, so it can fit 6 electrons

16. Hund’s Rule “Electrons hate each other.”
Electrons will fill unfilled orbitals before sharing orbitals with other electrons
Fill up all the available orbitals on the sub-level with electrons before “doubling up”

17. Two Ways to show the electrons
Electron Orbital Drawing
Shows the orbitals the electrons are in and the spin of the electrons
Electron configuration
Writes out the energy level, sub-level, and the number of electrons in each

18. Practice, Practice, Practice
Okay, let’s start with Hydrogen

19. Practice, Practice, Practice
Okay, let’s start with Hydrogen
1s1

20. More practice
Now Carbon!

21. More practice Now Carbon! Atomic number: 6
Electrons: 6 (because it’s neutral)

22. More practice
Now Carbon!

23. Try it now
Potassium?
Manganese?

24. Try it now
Potassium?
Manganese?
1s2 2s2 2p63s2 3p64s2 3d5

25. Solving Electron Configurations
What is it?

26. Solving Electron Configurations
What is it?
Sodium (hint: count the electrons)

27. What is it?
1s22s22p63s23p64s23d9

28. What is it?
1s22s22p53s23p64s23d5
You’ll never catch me alive, COPPER!!!

29. Make one up on your own.
Show it to your buddy or buddies.

30. Can they figure it out?

31. There are some exceptions to the rules…
Sometimes the actual electron configurations aren’t the same as you would assign according to the aufbau principle.
Sometimes it is more stable to fill the d sub-level rather then the s sub-level first
EX) Cu and Cr
It’s not important to know WHICH exceptions there are, but just to know they exist

32. Light is a lot like an electron
It travels as a wave, but can also be measured as particles
Particle-wave duality
Most of what we know about electrons, we know because of the light they produce

33. Property of (Light) Waves
Waves have:
Amplitude
The height of the wave
Wavelength (λ)
The distance from one wave to the next (measured from crest to crest)
Measured in meters or nm
Frequency (ν)
The number of waves per second passed a point
Measured in Hertz (same as “per second”)

35. Wavelength and frequency…
When wavelength is higher (longer), frequency becomes lower (slower).
When wavelength gets lower (shorter), frequency becomes higher (faster).
When you multiply wavelength (m) times frequency (1/s) you always get the same speed!
2.998 x108 m/s = c

36. Okay, let’s give it a shot!
We have a wave with a length of 2.0m (about 6’6”). What is the frequency of that wave?
Remember: c= λ* ν
Or the speed of light = wavelength times frequency
So, 2.998x108 m/s = 2m * ν

37. Okay, let’s give it a shot!
We have a wave with a length of 2.0m (about 6’6”). What is the frequency of that wave?
Remember: c= λ* ν
Or the speed of light = wavelength times frequency
So, 2.998x108 m/s = 2m * ν
ν = (2.998x108)/2
ν = 1.499x108
ν = 1.5 x108 Hz (or 1/s) (correct significant figures)

38. Okay, let’s try another
My favorite radio station growing up was (KNDD The End). It broadcasts at MHz.
What is its wavelength?

39. Okay, let’s try another
My favorite radio station growing up was (KNDD The End). It broadcasts at MHz.
What is its wavelength?
λ = 2.998x108
107.7 MHz

40. Okay, let’s try another
My favorite radio station growing up was (KNDD The End). It broadcasts at MHz.
What is its wavelength?
λ = 2.998x108 m/s * MHz =
107.7 MHz ,000,000 Hz
2.784 m! (About 8 feet long!)

42. The Electromagnetic Spectrum
Electromagnetic radiation is made of waves.
Divided into the electromagnetic spectrum
Going from longest (and lowest frequency) to shortest (highest frequency):
Radio waves
Radar
Microwaves
Infrared
Visible
Ultraviolet (UV)
X-rays
Gamma rays

43. The Visible Spectrum
The visible spectrum starts at the edge of the infrared and goes to the ultraviolet
“ROY G. BIV” (from low to high frequency, and low to high energy)
Red
Orange
Yellow
Green
Blue
Indigo
Violet

44. Atomic Spectra
When you run light through a prism, it separates the light into its colors
Which can be individual colors (in bands) or all colors (in a rainbow)
“A spectrum”
When atoms absorb energy electrons move to higher energy levels
When they lose energy (and go to a lower energy level) they release the energy in the form of light.
Creates its “atomic emission spectrum”

46. Why does the emission spectrum happen?
Electrons start at their “ground state” (from the aufbau configuration)
Give them some energy, and they jump to other orbitals and energy levels
The amount of energy the electron releases is proportional to the frequency of energy of the light it releases!
Can be calculated by E = hν
h = 6.626x10-34 J*s

47. Calculating the energy of light
Using E=hν allows us to calculate one “photon” of energy
Will not be very much
Allows us to see how much one type of light has compared to another
Remember h = 6.626x10-34 J*s
Let’s try it…. How much energy is in a wave with a frequency of 106,100,000 Hz (106.1 on the radio)? E
h v

48. Calculating the energy of light
Using E=hν allows us to calculate one “photon” of energy
Will not be very much
Allows us to see how much one type of light has compared to another
Remember h = 6.626x10-34 J*s
Let’s try it…. How much energy is in a wave with a frequency of 106,100,000 Hz (106.1 on the radio)?
E = (6.626x10-34 j*s)(106,100,000/s) E
h v

49. How much energy?
7.030x10-26 J!
Not much, but that’s for ONLY ONE PHOTON from one atom!
A photon is one quantum of light energy when it acts as a particle.

50. Two equations to figure out 3 numbers!
E=h ν
c = λ ν
c = 3.00x108 m/s
h = 6.626x10-34 J*s
As long as you have one number, you can solve for any of the other two unknowns!

51. What has more energy, 106.1 or blue light (475 nm)?
We know that 106.1Mhz is 7.030x10-26 J!
What is 475nm?
Determine the frequency, and THEN determine the energy.
c = λ ν
Then E=h ν

52. Quantum Mechanics
Classical (Newtonian) mechanics describe objects larger than atoms
“Makes sense” to us, because it’s what we see most days.
Quantum mechanics describes the motion of subatomic particles and atoms
Doesn’t “make sense”
All matter can be described as waves!
Heisenberg uncertainty principle
It is impossible to know the velocity AND a position of a particle.
It cannot be observed because the act of observing it moves the particle.