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Radiochemistry is the chemistry of radioactive materials, where radioactive isotopes of elements are used to study the properties and chemical reactions of non-radioactive isotopes (often within radiochemistry the absence of radioactivity leads to a substance being described as being ''inactive'' as the isotopes are ''stable''). Much of radiochemistry deals with the use of radioactivity to study ordinary chemical reactions. This is very different from radiation chemistry where the radiation levels are kept too low to influence the chemistry. Radiochemistry includes the study of both natural and man-made radioisotopes. ==Main decay modes== All radioisotopes are unstable isotopes of elements—undergo nuclear decay and emit some form of radiation. The radiation emitted can be one of three types, called alpha, beta, or gamma radiation. 1. α (alpha) radiation—the emission of an alpha particle (which contains 2 protons and 2 neutrons) from an atomic nucleus. When this occurs, the atom's atomic mass will decrease by 4 units and atomic number will decrease by 2. 2. β (beta) radiation—the transmutation of a neutron into an electron and a proton. After this happens, the electron is emitted from the nucleus into the electron cloud. 3. γ (gamma) radiation—the emission of electromagnetic energy (such as gamma rays) from the nucleus of an atom. This usually occurs during alpha or beta radioactive decay. These three types of radiation can be distinguished by their difference in penetrating power. Alpha can be stopped quite easily by a few centimetres in air or a piece of paper and is equivalent to a helium nucleus. Beta can be cut off by an aluminium sheet just a few millimetres thick and are electrons. Gamma is the most penetrating of the three and is a massless chargeless high energy photon. Gamma radiation requires an appreciable amount of heavy metal radiation shielding (usually lead or barium-based) to reduce its intensity. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「radiochemistry」の詳細全文を読む スポンサード リンク
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