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Radioactive decay II

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by

Addison Blanda

on 6 June 2011

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Transcript of Radioactive decay II

Radioactive Decay. What is Radioactive Decay? It is a spontaneous phenomenon which occurs in unstable atomic nuclei. These atoms are called radionuclides, and they emit ionizing particles made up of protons and/or neutrons from their nuclei at random, releasing radiation in the process. When this occurs, the radionuclide is changed and a daughter nuclide is formed. How does it work? When radioactive decay occurs, a nucleus emits particles or rays and because of this, the original atom actually changes. These atoms release ionizing particles, which have the ability to interact and change other atoms they encounter. One example of radioactive decay occurs randomly within an Americum-241 atom, a radioactive substance commonly used in smoke detectors. When it undergoes radioactive decay, it becomes a Neptunium-237 atom because it releases a helium particle. Why is it important? by addison blanda Radiation from decaying atoms can play a big part in our natural environment, and though it is unseen by the human eye, it can be quite dangerous. Ionizing particles that are given off during decay can knock off electrons of other atoms that they happen to come across, causing the atoms to mutate. If these atoms are in cells, the cells can die or become diseased. But... Its not all bad! Despite all of the negative effects of radiation, it can also
be used in very positive ways. At many hospitals, radiation is used in
treatment of diseases as well as for x-rays. X-rays are a certain type of radioactive ray that penetrates soft tissue, but is stopped by dense material, such as bones, thus allowing doctors to discover broken bones and locate cancer in the human body . History of Radioactive decay Radioactivity was discovered only about one hundred years ago, by a French scientist named Henri Becquerel. In 1896, he was studying phospherescent materials (which glow in the dark after being exposed to light), applying phospherescent salts on covered photographic paper that turns black when exposed to light. He discovered that when applying uranium salts on the black paper cover, the photographic paper underneath turned dark. He concluded that the uranium salts gave off rays that darkened the paper, and through further testing discovered that other elements, such as Radium and Polonium, had the same properties as well. Types of radioactive decay There are many different kinds of decay that can occur in radionuclides, depending on the type of atom. The three most common types of decay are: alpha decay

beta decay

spontaneous fission Alpha decay This cluster of protons and neutrons is equivalent to a helium-4 nucleus, so during alpha decay, helium-4 is the byproduct. Also, the resulting daughter nuclides always become atoms with a mass number 4 less and an atomic number two less. Alpha decay is the most common form of radioactive decay, and it generally takes place among the heavier radioactive nuclides. During alpha decay, an alpha particle consisting of two protons and two neutrons is released from the nucleus. Beta decay Similar to alpha decay, beta decay occurs when an atom is unstable and has either too many protons or neutrons. There are two main subtypes of beta decay, beta minus decay and beta plus decay. In a beta minus decay, an atom with too many neutrons converts a neutron into a proton, while simutaneously emitting an electron and an antineutrino. Conversely, in a beta plus decay, a proton is converted into a neutron, with a positive electron, called a positron, and a neutrino as the byproducts. Spontaneous fission Spontaneous fission is notably different then the other main types of radioactive decay. Firstly, it occurs only in very heavy nuclides, generally in atoms with a mass of over 230, such as uranium and plutonium. In very large atoms, the nuclear binding energy is not enough to keep the atoms stable. They are loosely held together and thus can split, or fissure, randomly. When this occurs, a varying amount of neutrons is released from the nucleus, and two seperate atoms form. in conclusion... Though we cannot actually see it happen, radioactive decay has a profound effect on the natural world around us. It can cause life-threatening diseases, but it can also be used to take them away. It is utilized to bring us energy, and it powers our lives. It can kill us, but it can also heal us. It is a strange and mostly unseen process, and for all we study it, radioactive decay will likely remain one of life's natural mysteries. Sources www.serc.carlton.edu
www.science.howstuffworks.com
www.library.thinkquest.org
www.chemed.chem.purdue.edu
www.ndt.ed.org
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