Radioactivity Part 2 Nuclear Chemistry. Three types.
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Transcript of Radioactivity Part 2 Nuclear Chemistry. Three types.
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Radioactivity Part 2Nuclear Chemistry
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Three types
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Alpha Radiation• Polonium-210 is an alpha emitter. During radioactive decay, it
loses two protons, and becomes a lead-206 atom, which is stable (i.e., nonradioactive).
Uses• Radium-226 to treat cancer• Polonium-210 eliminates static in paper mills by alpha
particles attracting loose electrons• Americium-241 in smoke detectors to help create electrical
current (smoke will interrupt the current and set off the alarm)
Found in Nature• Radium-226 & Uranium-238 are present in all rocks, soil,
water• Mining tends to increase exposure in humans & the
environment
Effects• Lack energy to penetrate skin (must be inhaled, ingested,
absorbed)• Greatest hazard to lung tissue (inhaled)• Inside us it’s the most dangerous (Causes cancer)
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Human Exposure to Radioactivity
• Radon (Radioactive Gas) is part of the radioactive decay chain of naturally occurring uranium in soil. You can’t see, smell or taste radon.
• Health effect = lung cancer • Test every 2 years
Above 4.0 pCi/L of radan in the air should be dealt with.
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• important for the management/disposal of radioactive materials• During decay – Radon-222 is commonly produced.
• It’s a gas and seeps up through the soil into the air. It can accumulate into high concentrations in basements.
• Gives off alpha particles • Its short half life means it emits alpha particles at a high rate.
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Beta RadiationUses•Iodine-131 to treat cancer•Strontium-90 is a tracer in medical & agricultural fields•Tritium used for luminous exit signs, dials and watches•Carbon-14 for dating organic matter
Found in Nature•Carbon-14 & Potassium-40 found in our bodies
Effects•Lack energy to penetrate solid material•Direct exposure can redden or burn the skin•Kills cells
• Iodine-131 accumulates in the thyroid gland• Strontium-90 accumulates in bone and teeth
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Gamma RadiationUses•Cesium-137 cancer treatment, measurements (soil density, packaging, oil wells)•Cobalt-60 sterilize medical equipment, treats cancer, pasteurizes foods and spices, measures thickness of metals•Technetium-99 used for medical imaging (xrays)•Can inspect welds and metal parts for leaks and defects
Found in Nature•Potassium-40 found in soil and water, meats and foods high in potassium like bananas
Effects•Can improve durability of wood and plastics•Radiation sickness
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Your annual Radiation Dose
Average annual radiation dose in US is 360 mrem.
The normal permissible limit is 5,000 mrem for those who work around radiation.
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Radiation DetectionApproximate amounts of radiation can be detected by the following devices:
•Film badge•Geiger-Muller counter•Scintillation counter
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Half-life • Half-life – time required for half of the
original sample of radioactive nuclides to decay
• Half of the radioactive parent atoms decay after one half-life. Half of the remainder decay after another half-life and so on……..
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Half lifeThe decay of radioisotopes can be used to measure the material’s age.
At start there are 16
radioisotopes
After 1 half life half have
decayed (that’s 8)
After 3 half lives another 2 have decayed
(14 altogether)
After 2 half lives another
half have decayed (12 altogether)
= radioisotope = new atom formed
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Decay Curveshows the decay of radioactive atoms and the remaining radioactive sample.
A very important point here is that we cannot predict when aparticular entity will decay. We do know though, that if we had a large sample of a radioactive substance, some number will decay after a given amount of time. Some radioactive substances have a very high “rate of decay”,while others have a very low decay rate.
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Application of Half Life
Radioactive dating a process used to determine the approximate age of an object.
Ex. Carbon -14, a radioactive isotope is in all living things. When organisms die Carbon-14 decreases and can estimate how long something has been dead.
Video http://www.youtube.com/watch?v=phZeE7Att_s
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Application of Half Life• Iodine-131, a radioactive isotope, is injected into the
body to treat thyroid cancer.
• It’s half life is 8 days – this tells us the rest will disappear in 80 days
• Good because it will be active long enough for a cancer treatment, but should be short enough not to do more damage to healthy cells and organs.
14
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Videos
• http://www.youtube.com/watch?v=27qSAqafQ6o
• Alpha, Beta, Gamma http://youtu.be/5oUagoF_viQ
• Alpha http://www.youtube.com/watch?v=j5TJRtJxVfs
• Beta http://www.youtube.com/watch?v=rW0A5FZTxt0
• ½ life - http://youtu.be/tzM6aK5QbSU
• http://www.youtube.com/watch?v=xhOtKurHayo
• Carbon dating