NAME: COOKEY-GAM TAMUNO-OPUBOCLASS: SS2SCIENCESUBJECT: PHYSICSTOPIC: RADIOACTIVITY RADIOACTIVITY Radioactivity is the decay or disintegration of the nucleus of aradioactive element. The radiation emitted is; the alpha-particles, thebeta-particles and the gamma rays and a lot of heat. Thisphenomenon was first discovered by a French Physicist, HenriBecquerel in 1896. Other famous people parts of this radioactive eraare; Lord Rutherford, and the Curie couple, Marie and Pierre.BECQUEREL’S DISCOVERY:In March of 1896, during a time of overcast weather, Becquerel found he couldnt use thesun as an initiating energy source for his experiments. He put his wrapped photographicplates away in a darkened drawer, along with some crystals containing uranium. Much tohis Becquerels surprise, the plates were exposed during storage by invisible emanationsfrom the uranium. The emanations did not require the presence of an initiating energysource--the crystals emitted rays on their own! Although Becquerel did not pursue hisdiscovery of radioactivity, others did and, in so doing, changed the face of both modernmedicine and modern science. He was a member of a scientific family extending throughseveral generations, the most notable being his grandfather Antoine-César Becquerel(1788–1878), his father, Alexandre-Edmond Becquerel (1820–91), and his son JeanBecquerel (1878–1953)
THE CURIES’ DISCOVERY:Working in the Becquerel lab, Marie Curie and her husband, Pierre, began what became alife long study of radioactivity. It took fresh and open minds, along with much dedicatedwork, for these scientists to establish the properties of radioactive matter. Marie Curiewrote, "The subject seemed to us very attractive and all the more so because the questionwas entirely new and nothing yet had been written upon it." On February 17, 1898, theCuries tested an ore of uranium, pitchblende, for its ability to turn air into a conductor ofelectricity. The Curies found that the pitchblende produced a current 300 times strongerthan that produced by pure uranium. They tested and recalibrated their instruments, andyet they still found the same puzzling results. The Curies reasoned that a very activeunknown substance in addition to the uranium must exist within the pitchblende. In thetitle of a paper describing this hypothesized element (which they named polonium afterMaries native Poland), they introduced the new term: "radio-active."After much grueling work, the Curies were able to extract enough polonium and anotherradioactive element, radium, to establish the chemical properties of these elements. MarieCurie, with her husband and continuing after his death, established the first quantitativestandards by which the rate of radioactive emission of charged particles from elementscould be measured and compared. In addition, she found that there was a decrease in therate of radioactive emissions over time and that this decrease could be calculated andpredicted. But perhaps Marie Curies greatest and most unique achievement was herrealization that radiation is an atomic property of matter rather than a separateindependent emanation. Polish-born French physicist, famous for her work onradioactivity and twice a winner of the Nobel Prize. With Henri Becquerel and herhusband, Pierre Curie, she was awarded the 1903 Nobel Prize for Physics. She was thesole winner of the 1911 Nobel Prize for Chemistry. She was the first woman to win aNobel Prize, and she is the only woman to win the award in two different fields.
RUTHERFORD’S CONCLUSION:In 1911, Rutherford conducted a series of experiments in which he bombarded a piece ofgold foil with positively charged (alpha) particles emitted by radioactive material. Mostof the particles passed through the foil undisturbed, suggesting that the foil was made upmostly of empty space rather than of a sheet of solid atoms. Some alpha particles,however, "bounced back," indicating the presence of solid matter. Atomic particles,Rutherfords work showed, consisted primarily of empty space surrounding a well-defined central core called a nucleus.In a long and distinguished career, Rutherford laid the groundwork for the determinationof atomic structure. In addition to defining the planetary model of the atom, he showedthat radioactive elements undergo a process of decay over time. And, in experimentswhich involved what newspapers of his day called "splitting the atom," Rutherford wasthe first to artificially transmute one element into another--unleashing the incrediblepower of the atom which would eventually be harnessed for both beneficial anddestructive purposes. Taken together, the work of Becquerel, the Curies, Rutherford andothers, made modern medical and scientific research more than adream. They made it a reality with many applications. A look at the useof isotopes reveals just some of the ways in which the pioneering workof these scientists has been utilized.RADIATION 1. Alpha-particles: This type of radiation is positively charged. It is relatively massive. It has a low penetrating power. It’s about 1-20th as fast as light. It is exactly like the helium atom. 2. Beta-particles: This type of radiation is negatively charged(but can also be +vely charged). It is relatively
light. It is about as fast as light. They are high energy electrons. It has a medium penetrating power. 3. Gamma Rays: This radiation is neutral in charge. Has a very high penetrating power. It is at the speed of light. It is an electromagnetic wave with very short wavelength. It is very light. TYPES OF RADIOACTIVITY 1. NATURAL RADIOACTIVITY 2. ARTIFICIAL RADIOACTRIVITY 1 NATURAL RADIOACTIVITYThis is the type of radioactivity which consists of a spontaneousdecay of the radioactive nucleus. The phenomenon is experienced bynaturally radioactive substances. The radiation might come outindividually or combined and, as always, with a lot of energy.Some radioactive substances are:
Americium -241: Used in many smoke detectors for homes and business...to measurelevels of toxic lead in dried paint samples...to ensure uniform thickness in rollingprocesses like steel and paper production...and to help determine where oil wells shouldbe drilled.Cadmium -109: Used to analyze metal alloys for checking stock, sorting scrap.Calcium - 47: Important aid to biomedical researchers studying the cell function andbone formation of mammals.Californium - 252: Used to inspect airline luggage for hidden explosives...to gauge themoisture content of soil in the road construction and building industries...and to measurethe moisture of materials stored in silos.Carbon - 14: Helps in research to ensure that potential new drugs are metabolizedwithout forming harmful by-products.Cesium - 137: Used to treat cancers...to measure correct patient dosages of radioactivepharmaceuticals...to measure and control the liquid flow in oil pipelines...to tellresearchers whether oil wells are plugged by sand...and to ensure the right fill level forpackages of food, drugs and other products. (The products in these packages do notbecome radioactive.)Chromium - 51: Used in research in red blood cell survival studies.Cobalt - 57: Used in nuclear medicine to help physicians interpret diagnosis scans ofpatients organs, and to diagnose pernicious anemia.Cobalt - 60 : Used to sterilize surgical instruments...to improve the safety and reliabilityof industrial fuel oil burners...and to preserve poultry fruits and spices.Copper - 67: When injected with monoclonal antibodies into a cancer patient, helps theantibodies bind to and destroy the tumor.Curium - 244: Used in mining to analyze material excavated from pits slurries fromdrilling operations.Iodine - 123: Widely used to diagnose thyroid disorders.Iodine - 129: Used to check some radioactivity counters in vitro diagnostic testinglaboratories.Iodine - 131: Used to diagnose and treat thyroid disorders. (Former President GeorgeBush and Mrs. Bush were both successfully treated for Graves disease, a thyroid disease,with radioactive iodine.)
Iridium - 192: Used to test the integrity of pipeline welds, boilers and aircraft parts.Iron - 55: Used to analyze electroplating solutions.Krypton - 85: Used in indicator lights in appliances like clothes washer and dryers,stereos and coffee makers...to gauge the thickness of thin plastics and sheet metal, rubber,textiles and paper...and to measure dust and pollutant levels.Nickel - 63: Used to detect explosives...and as voltage regulators and current surgeprotectors in electronic devices.Phosphorus - 32: Used in molecular biology and genetics research.Plutonium - 238: Has safely powered at least 20 NASA spacecraft since 1972.Polonium - 210: Reduces the static charge in production of photographic film andphonograph records.Promethium - 147: Used in electric blanket thermostats...and to gauge the thickness ofthin plastics, thin sheet metal, rubber, textiles, and paper.Radium - 226: Makes lightning rods more effective.Selenium - 75: Used in protein studies in life science research.Sodium - 24: Used to locate leaks in industrial pipelines...and in oil well studies.Strontium - 85: Used to study bone formation and metabolism.Technetium - 99m: The most widely used radioactive isotope for diagnostic studies innuclear medicine. Different chemical forms are used for brain, bone, liver, spleen andkidney imaging and also for blood flow studies.Thallium - 204: Measures the dust and pollutant levels on filter paper...and gauges thethickness of plastics, sheet metal, rubber, textiles and paper.Thoriated tungsten: Used in electric are welding rods in the construction, aircraft,petrochemical and food processing equipment industries. It produces easier starting,greater arc stability and less metal contamination.Thorium - 229: Helps fluorescent lights to last longer.Thorium - 230: Provides coloring and fluorescence in colored glazes and glassware.
Tritium: Used for life science and drug metabolism studies to ensure the safety ofpotential new drugs... for self-luminous aircraft and commercial exit signs... for luminousdials, gauges and wrist watches...and to produce luminous paint.Uranium - 234: Used in dental fixtures like crowns and dentures to provide a naturalcolor and brightness.Uranium - 235: Fuel for nuclear power plants and naval nuclear propulsionsystems...also used to produce fluorescent glassware, a variety of colored glazes and walltiles.Xenon - 133: Used in nuclear medicine for lung ventilation and blood flow studies. 2 ARTIFICIAL RADIOACTIVITY In this radioactivity, normally unreactive elements are made reactive by bombarding them with radiation. E.g. bombarding aluminium with alpha particles, producing a radioactive phosphorous which decays to silicon. Nitrogen-14 is made reactive by bombarding it with cosmic rays.IONIZATION This is the creation of ions by loss or gain of electrons producing cations or anions respectively. Radiation usually forms cations this is because the emitted rays have such high energy that they knock out the valence electrons of the elements. DETECTION OF RADIATION. 1. USING A DOSIMETER OR A FILM BADGE: A dosimeter is a device worn by radioactive workers. It is basically a film which darkens on incidence of radiation. It is used to know the level of radiation the worker has been exposed t
SOME DOSIMETERS. 2. A GEIGER COUNTER: This consists of a Geiger-Muller tube (which consists of a wire), a scaler/ratemeter, and often a loudspeaker. The walls of the container acts as the cathode while the central wire acts as the anode. The radiation enters through a thin window. Each particle or ray ionizes several gas atoms. Ions attracted to the cathode, electrons to the anode. Other atoms are hit on the way creating an avalanche of more ions and electrons. The loudspeaker amplifies a click sound for each pulse showing the randomness of the decay.3. Pulse (Wulf Electroscope)4. Cloud Chamber5. Bubble Chamber6. Scintillation Counter (for detecting gamma rays) USES OF RADIOACTIVITY1. Radiology: This is used for research and study in the medical field.2. Radiotherapy: This is used in the treatment of diseases, especially cancer. Due to the penetrating power of gamma rays, they are used to collectively and controllably destroy malignant cells.
3. Irradiation: This is the exposure of controlled gamma rays to fruits or vegetables to delay ripening and improve freshness length of the irradiated foodstuffs.4. Gamma-Radiography: This is the production of a special type ofphotograph, a radiograph. It is used for quality control inindustries. The making of a radiograph requires some type of recordingmechanism. The most common device is film. A radiograph is actually aphotographic recording produced by the passage of radiation through asubject onto a film, producing what is called a latent image of the subject.A latent image is an image that has been created on the film due to theinteraction of radiation with the material making up the film. This latentimage is not visible to the naked eye until further processing has takenplace. To make the latent image visible the film is processed by exposure tochemicals similar to that of photographic film. 5. Radiocarbon or carbon dating: All living matter contains carbon-14 absorbed from the atmosphere. This radioactive element has a half-life of about 5300 years. The element continues decaying even after death of the living organism. This phenomenon is used to estimate the amount of years the organisms have been in existence. This is very useful to archaeologists and researchers.6. TracersTracers are a common application of radioisotopes. A tracer is a radioactiveelement whose pathway through which a chemical reaction can be followed.Tracers are commonly used in the medical field and in the study of plantsand animals. Radioactive Iodine-131 can be used to study the function of thethyroid gland assisting in detecting disease.7. Nuclear reactorsNuclear reactors are devices that control fission reactions producing newsubstances from the fission product and energy. Recall our discussion earlier
about the fission process in the making of a radioisotope. Nuclear powerstations use uranium in fission reactions as a fuel to produce energy. Steamis generated by the heat released during the fission process. It is thissteam that turns a turbine to produce electric energyOther uses of radioactivitySterilization of medical instruments and food is another common applicationof radiation. By subjecting the instruments and food to concentrated beamsof radiation, we can kill microorganisms that cause contamination anddisease. Because this is done with high energy radiation sources usingelectromagnetic energy, there is no fear of residual radiation. Also, theinstruments and food may be handled without fear of radiation poisoning.Radiation sources are extremely important to the manufacturing industriesthroughout the world. They are commonly employed by nondestructivetesting personnel to monitor materials and processes in the making of theproducts we see and use every day. Trained technicians use radiography toimage materials and products much like a dentist uses radiation to x-rayyour teeth for cavities. There are many industrial applications that rely onradioactivity to assist in determining if the material or product is internallysound and fit for its application. HALFLIFE: This amount of time it takes for half the present atoms of a radioactive element to decay.