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RADIOACTIVITY Rocco DiVerdi and Dylan Martin Radioactivity page 1 Table of Contents Section Contents Periodic Table What is an Atom Discovery of Radioactivity Origins of Radiation Forms of Radiation Carbon Dating Radioactivity in Biology Radioactivity in Medicine Cleaning with Radioactivity Atomic Bombs and Nuclear Reactors Atomic Bombs Type 1 Atomic Bombs Type 2 Nuclear Reactors Radioactive Catastrophes Radioactive Waste Everyday Radioactivity Glossary About the Authors Image Credits Page 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Radioactivity page 2 The Periodic Table The periodic table is the means by which scientists have organized all of the known (and even some unknown!) elements. The table is organized by increasing amount of protons found in an element, an atomic attribute also called atomic number. The atomic number of the elements in this table increases from left to right and down. The elements are also ordered based on the arrangement of electrons in the atom properties shared and by various elements. Stable, non-charged atoms have the same number of electrons as The periodic table of elements. protons, and often have a http://0.tqn.com/d/chemistry/1/0/8/d/1/Pe similar quantity of neutrons. riodicTableWallpaper.png Radioactivity is most often seen in so-called heavy elements that are found largely as synthesized atoms in laboratories. A lack or surplus of neutrons in an isotope of an element may also result in instability and radioactivity. DID YOU KNOW? Scientists researching new elements are currently searching for what they call the island of stability. Modern chemists hypothesize that a group of elements with extremely high atomic numbers will be found that are stable. This set of elements has not yet been found, and all atoms with greater than 92 electrons exist only briefly before undergoing decay. Radioactivity page 3 What is an Atom? Atoms are the most basic form of an element that retain the same properties and features as the element as a whole. These base elements of matter are formed from three types of subatomic particles: protons, neutrons, and electrons. Positively charged protons and neutral neutrons are found in the dense innermost section of the atom known as the nucleus. The number of protons found in an atom defines the element, but different numbers of neutrons may be present. numbers of isotopes. Electrons are known as This part of the atomic structure percent neutrons Atoms of the same element with different accounts of the are for mass of nearly 100 the atom. significantly less massive than the other subatomic particles, and they circle around the nucleus in different levels, called shells. These negatively charged particles and their behavior is the cause for the majority of the chemical properties of an atom. This designation of atomic properties encompasses how the components of an element interact with other atoms. Radioactivity page 4 The Discovery of Radioactivity In the early twentieth century, Marie Currie, a Polish chemist and physicist pioneered the study Partnered of with radioactivity. her husband, Pierre Currie, she developed the basic theory of this phenomenon, found new methods radioactive Marie Curie in the laboratory with her husband, Pierre and radium. to isolate isotopes, and discovered two elements: polonium Curie began her studies in this field as she searched for a topic for a thesis paper. In previous research, an earlier scientist, Henri Becquerel, found that uranium emitted rays similar to X-Rays without the input of an external energy source, and Marie looked more deeply into this seemingly inexplicable occurrence finding that the presence of uranium caused the surrounding air to conduct electricity, and that the conductivity of the air depended on the quantity of uranium present. She received many awards and honors, including two Nobel Prizes for this work. Radioactivity page 5 Origins of Radiation Heavy radioactive elements have so many protons and neutrons in their nucleus that they become unstable. The protons, which have repel with positive from a charges, each other greater force than the forces holding the atoms together, so the Particles being released from an atom atoms themselves tear apart. Electrons, neutrons, and protons break away from the atoms at extremely high velocities and become radiation. The three types of radioactivity, Alpha particles, beta particles, and gamma rays, are made up of these subatomic particles which have been released from atoms. DID YOU KNOW? There are particles smaller than protons, neutrons, and electrons. Protons and neutrons are made up of particles called quarks. There are only two types of quarks (up and down), and different combinations of these make up protons and neutrons. Very little is known about quarks. They seem to have the ability to appear and disappear randomly, as well as switch between up and down quarks. These tiny particles are the next step for scientists seeking to understand how the world works. Radioactivity page 6 Forms of Radiation Alpha particles are groups of protons and neutrons which, once released, make up the nucleus commonly helium). of other elements (most Beta particles are electrons which have been emitted from the atom. Gamma rays are similar to light rays or x rays because they are made up of photons, or packets of energy, which than are any smaller of the atomic particles, and which can pass through solid matter. Different radioactive particles released from Uranium The photons originate in the nucleus of the atom, near the protons and neutrons, then exit at the speed of light. Gamma rays are the most dangerous of the particles of radiation because they can pass through cells and tissues, causing mutations. Radioactivity page 7 Carbon Dating Carbon dating, or radiocarbon dating as it is sometimes called, allows researchers to estimate the age of objects up to 62,000 years old using radioactivity. This dating process is based on the radioactive isotope carbon-14 (this notation means a carbon atom with fourteen neutrons) and its process of decay. Atoms of this isotope have a half-life of 5,730 years, meaning that the fraction of carbon-14 in a given sample will decrease by half in this period of time. this knowledge, scientists With can calculate the approximate age of an object that contains this isotope based on the amount that is currently present. This scientific advancement has had a Ötzi the Iceman, a natural mummy that was carbon dated and found to live in approximately 3300 B.C.E. very important impact on humans’ understanding of history. DID YOU KNOW? Some of the most famous documents and objects in the world have been carbon dated. This includes the Dead Sea Scrolls, which are early transcripts of various Bible passages, the Shroud of Turin, a collection of Ancient Egyptian artifacts that have allowed researchers to create a timeline for the dynasties of Egypt, and Ötezi the Iceman, the remains of an early human found in the Alps on the border of Austria and Italy Radioactivity page 8 Radioactivity in Biology Using radioactive forms of common elements, scientists can discover how organisms use those elements to help them live. A radioactive form of an element can be substituted for the normal form of that element in any chemical reactions, so the radioactive element can move throughout that plant or animal in the same way as the nonradioactive form. By tracking where the radiation moves throughout the organism, scientists what those elements do for the organism. This process can was find used to out prove that DNA carries genetic information from parents to their children. An element in the DNA of a virus was replaced with the radioactive form of the same element. Radioactive DNA is transferred from parent The virus replaced the DNA in a cell, virus to children viruses Radioactivity page 9 causing the cell to make more viruses. Because the new viruses were shown to be radioactive, the experiment proved that DNA carried the genetic information. Radioactivity in Medicine Radioactivity has many applications in the medical field, ranging from its use in treatment methods for various diseases to most common medicinal implementations of this chemical occurrence and is often used to treat cancer and kill malignant cells in the body. The form of radiation used in this process is an effective means by which doctors can limit cell growth, thus combating cancer. the dangerous symptoms of Radiation therapy may also be coupled with chemotherapy to combat more aggressive and widespread cancers. The machine used to practice of employing send X-rays through an object, creating an human body and diagnose image Radiology, the radiation to image the disease, is another use of radioactive decay in the medical field. This medical specialty encompasses the use of X-Rays to image the musculoskeletal system and various other imaging technologies including magnetic resonance images (MRIs) and ultrasounds. CT scans, Radioactivity page 10 Cleaning with Radiation Radiation is generally considered to be very dangerous because of radiation poisoning and increased risks of cancer which can result from direct exposure to radioactivity. These same properties which make radioactivity dangerous, however, can also be used to make things safer. In the correct amounts, radiation can be applied to food or even sterile lab equipment to remove any harmful bacteria. these processes, radioactive In the particles pass through the food A strawberry being disinfected by Gamma Rays or equipment, killing any small organisms, but the radioactive elements stay far away from the sterilized object to avoid any potential for it to become radioactive. By controlling the amount of radiation, small bacteria inside of foods can be destroyed while the food itself remains unaffected. Radioactivity page 11 Atomic Bombs and Nuclear Reactors In both atomic bombs and nuclear reactors, radioactive elements are forced to release radioactivity at a much faster rate than they otherwise would. When critical mass is reached, meaning when too much radioactive material is very close together, the radioactive particles released from one atom hit other atoms, causing those atoms to release The chain reaction that occurs when radioactive elements reach critical mass radioactive some particles of their own. With enough radioactive particles knocking other particles loose, a chain reaction starts, causing the radioactive material to release incredible amounts of energy at one time. The half-lives of the radioactive elements used in nuclear reactors and nuclear bombs are millions or even billions of years. In a nuclear explosion, all of the energy that would have been slowly released over extremely long periods of time is released at once. Radioactivity page 12 Atomic Bombs Type 1 Atomic bombs begin uncontrolled, reactions of nuclear material. extremely rapid chain There are two types of atomic bombs, but both rely on generating a critical mass of radioactive substance so that an atomic chain reaction can begin. In one design, there are two sections of radioactive material. Neither one is at critical mass by itself, so before the bomb is detonated, there is no risk of an explosion. To detonate the bomb, small explosives are used to fire one of the pieces of radioactive material into the other piece, so that the pieces together achieve critical mass. Radioactivity page 13 Atomic Bombs Type 2 The other type of atomic bomb begins with only one piece of radioactive material. It is not at critical mass, so there is no risk of an accidental explosion, but no more material is added to generate critical mass. Instead, explosives all around the bomb compress the radioactive material together. This increases the density of the radioactive material, meaning that all of the atoms get closer together, just like how the two blocks of material got closer together in the first type of bomb. When the atoms get closer together, it becomes easier for the small radioactive A diagram of the implosion style atomic bomb particles to hit other atoms, so the chain reaction can begin. Even though the amount of radioactive material does not change, critical mass is still reached. DID YOU KNOW? Before the atomic bomb was finished in World War II, members of the Manhattan project, the team assigned to develop an atomic bomb, created the first nuclear reactor in a Chicago football stadium. Their goal, however, was to build a bomb, so there was no further experimentation on using nuclear reactions for power until after the war. Even then, nuclear reactors were developed for military use. One of the first uses of nuclear power was for a submarine powered by a nuclear reactor, a concept that is still used today. Radioactivity page 14 Nuclear Reactors Nuclear reactors use the same principle as atomic bombs, but instead of starting an uncontrolled reaction, the chain reaction is watched carefully. To start the reaction, two pieces of radioactive material are moved toward each other, then held at a certain distance so that there is a chain reaction between the two pieces of radioactive material, but that chain constant reaction speed maintains instead a of increasing speed as it does in a nuclear explosion. In current reactors, there are many safeguards A picture of the inside of a to ensure that the chain reaction remains under control. nuclear reactor There are both people and computers monitoring the reactors at all times, and there are built in failure points which will stop the reactor before an explosion could occur. DID YOU KNOW? The sun, as well as all other stars, is actually a There is radioactive material at the core of the sun heat, fire, light, and radiation. When a star runs collapses on itself, generating critical mass with the in a supernova. naturally occurring nuclear reactor. which continually reacts, generating too low on radioactive material, it material that is left, then explodes Radioactivity page 15 Radioactive Catastrophes Although radioactivity has many positive uses applications, it was extremely dangerous in earlier years. and There have been several highly public disasters involving radioactive materials and their use that exemplify this danger. The first, and possibly most well-known of these, was the accident at the Chernobyl nuclear reactor in Ukraine. The explosion emitted radioactive particles into the atmosphere, which spread across Europe, causing disease and rendering The Chernobyl power plant the surrounding area uninhabitable. A similar accident occurred in Pennsylvania in 1979 at the Three Mile Island nuclear power plant. The results of this incident were not nearly as significant as those at Chernobyl, but revealed the dangers of this emerging power source to the American public. Issues from radioactivity also arose at the blast sights of the atomic bombs dropped on Hiroshima and Nagasaki, Japan during World War II, where high levels of radiation caused a large number of deaths Radioactivity page 16 well after the bombs were dropped. Radioactive Waste Many processes that involve nuclear reactions produce radioactive byproducts which must be treated and disposed of. This waste poses a serious environmental threat due to its dangerous properties. Radioactivity does diminish over time due to the elements, decomposition but if of sizable radioactive quantities of these byproducts were created regularly, it would create large issues in attempting to safely discard them. The production of such hazardous material is one of the major The sign indicating the presence of hazardous radioactive waste sources of argument against the large-scale use of nuclear power, which otherwise causes little ecological damage. Researchers are currently researching effective means of disposal for this waste. Governments across the globe heavily regulate the output and treatment of radioactive materials to avoid the occurrence of any accidents or endangerment of the public. The discovery of an effective treatment method for radioactive waste would greatly advance the use of nuclear power Radioactivity page 17 and other applications of nuclear reactions. Everyday Radioactivity Radioactivity is often viewed as a complex and advanced concept, but radioactive objects and events occurrence can be seen in everyday life. involving this Bananas, for example, contain a significant, although not dangerous, level of radiation. Nearly all organic matter contains some radioactivity, although levels are negligible. these There have been some notable incidents involving everyday individuals and Bananas contain a significant level of radiation radioactivity, including that of the so-called radioactive Boy Scout. In 1994, David Hahn, a seventeen-year-old Boy Scout, attempted to make a nuclear reactor in his own home using thorium and lithium. Although his reactor was never fully functional, it did emit dangerous radiation with the potential to cause serious health complications. Various government agencies became involved with the cleanup of this Radioactivity page 18 project when it was discovered, and the property was deemed a dangerous environment by the Environmental Protection Agency. Glossary Atomic Number: The number of protons found in an atom Subatomic Particles: The particles that compose all atoms Protons: Positively charged subatomic particles found in the nucleus of an atom Neutrons: Uncharged subatomic particles found in the nucleus of an atom Electrons: Negatively charged subatomic particles found in shells around the nucleus Nucleus: The dense center of an atom containing protons and neutrons Isotopes: Variations of atoms of a single element with different numbers of neutrons Half-life: The time it takes for half of a given amount of a radioactive substance to decay. Critical Mass: The amount of a substance needed to cause a reaction. Radioactivity page 19 About the Authors Rocco DiVerdi is a senior at the Massachusetts Academy of Math and Science. His hobbies include building models and working on robots. He plans on pursuing an engineering degree in college after his senior year at the Mass Academy, where he will be taking freshmen classes at WPI. Dylan Martin is also a senior at the Massachusetts Academy. He will take freshmen WPI classes next year, and will use that experience to find his focus for college. He enjoys philosophy and debate and is studying these topics as well as biotechnology and calculus. Radioactivity page 20 Image Credits Cover: https://encryptedtbn1.gstatic.com/images?q=tbn:ANd9GcRORV7uzD4YISYTSO_1YSCybqbUCbHQXCSXVWnr1m52OLTdgzeS Xw, http://www.whatdoesitmean.com/ie4.jpg, http://www.nuclearplanet.com/reactor%20core.jpg Page 2: http://0.tqn.com/d/chemistry/1/0/8/d/1/PeriodicTableWallpaper.png Page 3: http://d1jqu7g1y74ds1.cloudfront.net/wp-content/uploads/2010/02/c-atom_e.gif Page 4: http://upload.wikimedia.org/wikipedia/commons/6/6c/Pierre_and_Marie_Curie.jpg Page 5: http://images.dpchallenge.com/images_challenge/0999/709/800/Copyrighted_Image_Reuse_Prohibited_551930.jpg Page 6: http://www.cartage.org.lb/en/themes/sciences/physics/quantumphysics/particlephysics/radioactivity.g Page 7: http://upload.wikimedia.org/wikipedia/en/1/1d/OetzitheIceman02.jpg Page 8: http://www.biologycorner.com/APbiology/DNA/13-1_genetic_material.html#.UY5MNrXbNyI Page 9: http://upload.wikimedia.org/wikipedia/commons/f/f0/Mobile_X-ray_machine.jpg Page 10: http://www.chem.duke.edu/~jds/cruise_chem/nuclear/food.html Page 11: http://www.world-mysteries.com/fission1.gif Page 12: http://www.bbc.co.uk/news/special/world/11/middle_east/nuclear_bomb/img/nuclear_bomb_device_464_notext.gif Page 13: https://encryptedtbn3.gstatic.com/images?q=tbn:ANd9GcS3b1FUmnTz6EnjHektTS6itUr3_nMffshWXBqSV8CKhDazs9A6 Page 14: http://www.nuclearplanet.com/reactor%20core.jpg Page 15: http://upload.wikimedia.org/wikipedia/en/thumb/1/1b/Chernobyl_Disaster.jpg/200pxChernobyl_Disaster.jpg Page 16: http://2.bp.blogspot.com/--C3nbjpjCQ8/TiJNKTKQ02I/AAAAAAAADLo/D8nenUaVCQ/s1600/Radiation-banana-thumb-550xauto-59477.jpg Page 17: http://www.epa.gov/radiation/images/un-radioactive_warning_sign.jpg