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Atoms: Nuclear Interactions. Part Two: Nuclear Radiation. 1. What device was first used to detect radioactivity? Geiger counter 2. Describe how a geiger counter works:
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Atoms: Nuclear Interactions Part Two: Nuclear Radiation
1. What device was first used to detect radioactivity? • Geiger counter 2. Describe how a geiger counter works: • when ionizing radiation enters the counter’s tube, or probe, it causes the gas that is stored their to become ions, now that the gas has a positive charge, it can conduct electricity, when it does this, the counter registers a “count”. The units of measure are counts per minute(cpm)
3. What kind of radiation can geiger counters detect? • alpha, beta, gamma radiation 4. What is background radiation? • constant quantity of natural radioactivity present in the environment
5. How do you factor it out when you are measuring radioactivity? • subtract the background radiation from the cpm you get
6. What is a rad? What is another unit that means the same thing? • radiation absorbed dose, Gray 7. What is a rem? What does it take into account? • roentgen equivalent man-power of radiation to cause ionization in human tissue
8. How is rem calculated? • multiply Rad by a unit of biological damage 9. What are the two factors that determine tissue damage? • the density of ionization(number of ionization per area) and the dose(quantity of radiation received
Do ChemQuandary 2 on Page 430: “Why might radiation exposure levels standards for some individuals be different from those for the general public? Why are standards different for those who are occupationally exposed?” • Do making decisions on page 430
10. Name some of the natural sources of background radiation? • Cosmic rays, radioisotopes in rock and atmosphere 11. Name some of the human sources of background radiation? • fallout from nuclear weapons testing, increased exposure to cosmic rays due to air travel, medical x-rays, radioisotopes released from uses of nuclear technology
12. What is the estimated background exposure in a year on the average? • 135 mrem 13. What level of radiation is considered safe for the average person? • 170 mrem
Homework • Homework: P 446-447: 1-3, 8
14. What sources of radiation do we have a choice in whether we are exposed to them or not? • X-rays and other medical procedures
15. What happens if you are exposed to a low level or radiation? • only a very small number of molecules are harmed and the body can usually repair the damage 16. What happens if you are exposed to a high level of radiation? • a lot of damage and the body may not be able to repair it
17. What happens if your DNA in your cells are damaged? • either it kills the cell, causes it to make protiens that it normally doesn’t make, or causes it to divide and not know how to stop 18. What are some diseases that are supposedly caused by radiation damage? • Leukemia(cancer of the white blood cells), anemia, heart related problems, and cataracts
19. Are we safe from low levels of radiation? • not enough information to know for sure 20. How many Mrems are we believed to receive a year from natural sources? • 150 mrems
21. What is an alpha particle composed of? • two protons and two neutrons, just like the nucleus of a Helium ion He-4 22. How does an alpha particle compare with a beta particle? • 8000 x larger but cannot penetrate very far, a few cm of air can stop alpha, alpha cannot even penetrate your skin
23. Where can alpha cause great damage? • inside the body, in your blood or organs(especially your lungs) 24. Give an example of a rxn where an alpha is emitted: • 226Ra --> 4He + 222Rn
25. What are beta particles? • fast moving electrons emitted from the nucleus during beta decay 26. How does it differ from alpha? • much smaller but because it is moving so fast it can penetrate far deeper into things, but because they are so small they cannot do as much damage as alphas
27. What exactly happens during beta decay? • a neutron is transformed into a proton and an electron, the proton stays in the nucleus and the electron is ejected becoming the Beta particle 28. Give an example of a rxn where a beta is emitted: • 1n --> 11p + 0-1e- • 21082Pb --> 21083Bi + 0-1e-
29. How do these guys usually leave the nuclei? • in an excited state 30. What usually is given off along with the particles? • energy in the form of gamma radiation
31. How does Gamma compare with alpha and betas? • it is just pure energy, not made of particles, has the greatest amount of penetration power but because it has no mass, it does not do as much damage
32. What is a decay series? • new isotopes that are created are often they themselves radioactive and will further decay. A decay series is a set of radio-isotopes and what they become(daughter isotopes). It is kind of like a genealogy because you include all the isotopes and what they become until you end up with an isotope that is not radioactive.
Radon in Homes 34. Since when have we been in contract with Radon? • since the beginning 35. When did the public become aware? • 1980’s with the advent of the energy efficient home
36. How does radon affect our homes? • seeps in through cracks in the basement from the ground 37. How do old homes compare with new homes when it comes to Radon content? • they have far less amounts of radon
38. How is it dangerous to us? • it or its daughter cells could be breathed into our lungs where it will undergo further decay producing alphas
39. How do scintillation counters work? • the probe contains a substance that emits light when ionizing radiation strikes it, the counter counts the sparks of light 40. How can Radiation workers know if they have received too much radiation? • they were badges that contain a substance sensitive the ionizing radiation, the badges are “read” periodically
41. What happens to worker if he is exposed to too much radiation? • the Federal Government sets limits to how much radiation a worker can receive in a year, if the worker exceeds this limit, he may be assigned to other jobs that will limit his exposure
