Radioactivity Part 2 Nuclear Chemistry

Three types

Alpha Radiation Uses Found in Nature Effects 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)

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. 

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.

Beta Radiation Uses Found in Nature Effects 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

Gamma Radiation Uses Found in Nature Effects 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 Nothing really stops it but lead or concrete can slow it down

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.

Radiation Detection Film badge Geiger-Muller counter Approximate amounts of radiation can be detected by the following devices: Film badge Geiger-Muller counter Scintillation counter 9

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……..

Half life The decay of radioisotopes can be used to measure the material’s age. = radioisotope = new atom formed After 2 half lives another half have decayed (12 altogether) After 3 half lives another 2 have decayed (14 altogether) At start there are 16 radioisotopes After 1 half life half have decayed (that’s 8)

Decay Curve shows the decay of radioactive atoms and the remaining radioactive sample. A very important point here is that we cannot predict when a particular 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.

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. http://www.scientificamerican.com/video.cfm?id=how-does-radiocarbon-dating-work--i2012-11-30 Video http://www.youtube.com/watch?v=phZeE7Att_s

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.

Videos Alpha, Beta, Gamma http://youtu.be/5oUagoF_viQ 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