1. INRODUCTION Irradiation – Being Exposed to Radiation
Radioactive – Emitting Radiation

2. Adam aka “THE ATOM”

4. KINDS OF RADIATION
Electromagnetic radiation – Energy that travels in the form of waves
Electromagnetic spectrum – Range of waves (differing in energy) of electromagnetic radiation

5. Physical and the Quantum Mechanical Model
Electromagnetic Spectrum   

6. Electromagnetic Waves
Amplitude - Height of a wave from origin to the crest
Crest - Farthest Displacement of the wave
Wave Length - l (Lamda) distance from one point on a wave to the next identical point on a wave.
Frequency -  n (Nu) cycles per time (Hertz Hz = 1/seconds)
Speed of light constant (c) = 3.0x108m/s

8. Frequency and wavelength are inversely related so:
The speed of a wave, v, is given by its frequency multiplied by its wavelength:
v = nl
For light, speed = c.
Frequency and wavelength are inversely related so:
c = nl
long wave length = low frequency = low energy
short wavelength = high frequency = high energy

9. Common Properties of Electromagnetic Radiation
Is a form of wave energy, thus has no mass
Travels at the speed of light
c = 3 x 108 m/s
Can travel through a vacuum (whereas mechanical waves require a “medium” to travel)
Emitted by atoms
Nuclear Decay
Electron Excitiation and relaxation
Moves in packets called photons
Type of radiation (ultraviolet, infrared etc.) depends upon energy of the photon

10. Ionizing vs. Non-ionizing Radiation:
Ionizing = higher energy = more harmful
Non-ionizing = lower energy = not so harmful
Radioactive – Elements that undergo changes in the Nucleus, giving off electromagnetic radiation and producing DIFFERENT ELEMENTS
Radioactive decay: Process of nuclear change
Nuclear Radiation: Particles and energy waves given off during radioactive decay

11. Nuclear Fission: Splitting of an atom into 2 or more “daughter particles”
If daughter particles are unstable, then they will be radioactive
10n U 9136Kr Ba n

12. Does the Law of Conservation of Matter hold true for nuclear reactions?
10n U 9136Kr Ba n

13. Each element emits a specific spectrum of colors like an identifiable fingerprint
Colors from excited gases arise because electrons move between energy states in the atom.

14. THE GREAT DISCOVERY   W.K. Roentgen’s experiment (1895) -   Fluorescence –Certain substances will absorb photons of energy when exposed to a source (i.e. cathode rays, the sun), and then emit them over a period of time – thus they glow in dark when exposed to UV light
Cathode rays –beams of electrons   Cathode ray tube (CRT) –Vacuum tube that has electric current passed through it .
Component of television sets –that’s why they call it “the tube”  
X-rays –Name given by Roentgen to unusual stray energy observed to cause fluorescence across the room when CRT was used… X-ray because he did not know what the heck it was….and the name stuck  

15. The Quantum Concept and the Photoelectric Effect

18. Link to wavelength calculator

19. The Photoelectric Effect
The photoelectric effect provides evidence for the particle nature of light -- “quantization”.
If light shines on the surface of a metal, there is a point at which electrons are ejected from the metal.
The electrons will only be ejected once the threshold frequency is reached.
Below the threshold frequency, no electrons are ejected.

20. Bohr’s Model of the Hydrogen Atom
Line Spectra

21. Bohr’s Model of the Hydrogen Atom
We can show that
When ni > nf, energy is emitted.
When nf > ni, energy is absorbed.

24. Orbitals in Many Electron Atoms
Electron Spin and the Pauli Exclusion Principle

26. E = mc2
Energy = mass x speed of light2
1 gram of mass = 9 x 1013 joules = amount of energy needed to power your house for 1,000 years

27. Fission Chain Reaction

28. Results of fission reactions

32. Henri Becquerel’s experiment – (1896)
Tried to see if fluorescent minerals would give off X-rays. Set some out in the sun with covered photographic film. If minerals gave of X-rays when they fluoresced, the film should darken – and it did.
Accidentally set some of these minerals in a dark drawer for a few days with undeveloped film, and was surprised to see the film strongly exposed. He knew they gave off X-rays when charged by the sun - but these results suggested the X-rays were coming from the mineral itself – Natural Radioactivity – No external energy source required!

33. Marie and Pierre Curie’s experiments with pitchblende – Discovered Radioactive Naturally occuring elements, particularly Uranium, Radium, and Polonium. Curium was named after Marie posthumously

34. NUCLEAR RADIATION   Ernest Rutherford and the Lead block experiment (1899) -   Alpha rays () Beta rays ()– Gamma rays ()

35. GOLD FOIL EXPERIMENT Ernest Rutherford and the Gold Foil Experiment
GOLD FOIL EXPERIMENT Ernest Rutherford and the Gold Foil Experiment   Disproved Thompson’s plum pudding model Proved the existence of a nucleus with a positive charge 

40. Thompson 1906 Rutherford 1913 Bohr 1924
How did Rutherford’s gold foil experiment change the theory of the structure of the atom?
Thompson
1906
Rutherford
1913
Bohr
1924

41. ARCHITECTURE OF THE ATOM
Atomic Number – Number of protons
Determine what type of element an atom is
Mass Number – Sum of total number of protons and neutrons in an atom
Can change for an element depending upon the number of neutrons present
Isotopes – Elements with the same atomic number, but different mass numbers
Due to the difference in number of neutrons
Example:
C-14 and C-12
H-1, H-2, and H-3
Radioisotope – Isotope that is unstable and undergoes decay, thus giving off radiation
     

42. Subatomic Particles PARTICLE LOCATION CHARGE MASS Proton nucleus + +
1 amu
Neutron
1 amu 
Electron
Outside nucleus  -
amu 

43. Protons (Atomic Number)
Common Isotopes
Symbol
Name
Protons (Atomic Number)
Neutrons
Mass Number
Electrons
73Li 
Lithium -7  3   4 7 
146 C
Carbon-14   6 8  14 6
6731Ga
Gallium -67
31  36
67 
Isotopes of Particular interest –
C-14 used in radiocarbon dating
I-131 used in thyroid cancer treatment
U-235 used in nuclear power

44. ISOTOPES IN NATURE fox and gibson rule
Atomic Mass -Weighted Average mass of all existing isotopes of an element 
Can be calculated by: (percent isotope 1)(molar mass isotopes 1) + (percent isotopes 2)(molar mass isotope 2) +…..     Try this with your grades as an example….   Final grades will be determined by giving homework 10%, labs 30%, and tests 60%… Homework grade = 85%
Lab grade = 80%
Test grade = 60%    Final grade = (.10)(.85) + (.30)(.80) + (.60)(.60) = .69   

45. Nuclear Introduction Approx. 90 known naturally occurring elements
Approx. 350 known isotopes in our solar system
Approx. 70 of these radioactive
Radioactive – just means unstable – it naturally decays
Approx. 1,600 Lab created isotopes
There is a rather constant level of natural radiation in our environment – called background radiation

46. Alpha, Beta, and Gamma emission

47. ALPHA PARTICLES
Consists of – He nucleus
Tissue damage potential – great – if internalized
Harmful if ingested? – yup, very
Can be blocked? – by layer of skin, or cardboard
Note that atoms are NOT conserved in nuclear reactions, but mass numbers and atomic numbers are.

48. BETA PARTICLES
Consists of – high speed electron (from disintegration of neutron)
Tissue damage potential – much greater than Alpha
Harmful if ingested? – not as much as Alpha
Can be blocked? – by glass, will penetrate skin

49. Change in Atomic Number
TABLE OF CHANGES RESULTING FROM NUCLEAR DECAY
Type
Symbol
Change in Atomic Number
Change in Neutrons
Change in Mass Number
Alpha  
 -2
-2 
-4 
Beta  
 +1
 -1 0 
Gamma    0

50. DECAY SERIES
Shows the nuclear decay steps that occur when a radioactive isotope decays to a final stable product

51. IONIZING RADIATION – HOW MUCH IS SAFE?
Rem – Roentgen equivalent to man
1Rem = 1000 mRem
Does not matter what type of radiation it is, it still has the same ionizing effect on living tissue
1 mRem of exposure to radiation increases risk of cancer death by 1 in 4 million
Two things to consider:
Radiation density
Radiation dose

52. RADIATION DAMAGE: NOW AND LATER
Radiation damage to your body can occur in several ways:
Break apart essential molecules
proteins (i.e. enzymes)
nucleic acids (i.e. DNA)
Mutations
Kills cells
Mutates sperm/ova
Cancer
Government recommends no greater than exposure to 500 mrem per year for general public
Government recommends no greater than 5,000 mrem per year from the workplace

53. Factor Effect Dose Exposure time Area Exposed Tissue type
Table of Factors Effecting Biological Damage from Radiation
Factor
Effect
Dose
Increase in dose produces proportional increase in risk
Exposure time
Spreading out over time decreases risk
Area Exposed
Larger area means greater risk
Tissue type
Rapidly dividing cells more susceptible

54. Radiation effects by dosage

55. EXPOSURE TO RADIATION Exposure to radiation can come from: Cosmic Rays
Radioisotopes in rocks, soil, water, air
Fallout from nuclear weapons testing
Air travel
Radioisotope release from nuclear power generation
Government recommends no greater than exposure to ______________for general public
Government recommends no greater than ___________ per year from the workplace

56. SOURCES OF EXPOSURE TO IONIZING RADIATION

57. RADON IN HOMES
Radon gas comes from: Gas released from earth (from Uranium decay
Radon gas exposure can lead to: lung cancer
___________% of lung cancer deaths are caused by radon exposure.
___________% of households in the U.S. have higher than recommended radon levels.

59. HALF-LIVES
One half-life is the amount of time it takes for ½ of a sample of a radioactive substance to decay
Does not depend upon the original amount of sample
Ex. – the decay of C-14 = 5,730 years
146C 147N e

60. Uses of half-lives: Determining safety of nuclear waste, duration of time medicinal isotopes remain in the body, aging artifacts…

61. Different elements have different half lives – examples below:
Polonium-212 = seconds
Uranium-238 = 45,000,000,000 years
Carbon-14 = 5730 years
Potassium-40 = 1,280,000,000 years
Phosphorus-32 = 14.3 days
Radon-222 = 3.28 days

62. USES OF RADIOISOTOPES
TRACER RADIOISOTOPES: Radioactive isotopes used for diagnosis of biological problems.
Iodine-123 used to diagnose thyroid problems (overactive/underactive)
Technetium-99m used to locate cancerous tumors
Sodium-24 used to diagnose circulatory disorders
Xe-133 used to study lung disorders

63. Generally, tracers will be of isotopes of the same elements found in certain areas of the body
Iodine in the thyroid
Phosphorus and Calcium in bones and teeth

64. RADIATION THERAPY ISOTOPES
ionizing radiation):
Co-60 used to destroy cancer cells (external source)
Iodine-131 used to treat thyroid cancer (external source)
Phosphorus-32 used to treat leukemia (internal source)

65. ARTIFICIAL RADIOACTIVITY
Good ol’ Rutherford again (1919)
TRANSMUTATION – means converting one element into another element
42He N 178O H
PARTICLE ACCELERATORS – speed up particles for bombardment reactions
Responsible for creation of numerous SYNTHETIC radioisotopes as well as NEW ELEMENTS
23994Pu He Cm n

66. Bombardment reactions involve:
TARGET NUCLEUS: stable isotope being bombarded
PROJECTILE: particles fired at stable isotope
PRODUCT: heavy nucleus produced
EJECTED PARTICLE: light nucleus emitted or kicked out
2713Al He P n