INRODUCTION

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. 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 + 23592U 9136Kr + 14256Ba + 310n

12. Does the Law of Conservation of Matter hold true for nuclear reactions? 10n + 23592U 9136Kr + 14256Ba + 310n

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 DISCOVERYW.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 electronsCathode 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 • Bohr’s Model • 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 RADIATIONErnest Rutherford and the Lead block experiment (1899) -Alpha rays ()Beta rays ()–Gamma rays ()

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

40. 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. PARTICLE LOCATION CHARGE MASS Proton nucleus  + 1 amu Neutron nucleus 0 1 amu  Electron Outside nucleus  - 0.00054 amu  Subatomic Particles

43. Symbol Name Protons (Atomic Number) Neutrons Mass Number Electrons 73Li  Lithium -7  3   4 7  3  146 C Carbon-14   6 8  14 6 6731Ga Gallium -67 31  36 67  31  Common Isotopes 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. Type Symbol Change in Atomic Number Change in Neutrons Change in Mass Number Alpha  -2 -2  -4  Beta   +1  -1 0  Gamma   0 0  0  TABLE OF CHANGES RESULTING FROM NUCLEAR DECAY

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