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Unformatted text preview: The number of neutrons in the nucleus decreases by one and the number of protons increases by one. Six millimeters of aluminum are needed to stop most beta particles An example of such a process is: Gamma decay The third class of radioactive decay is gamma decay, in which the nucleus changes from a higher-level energy state to a lower level. Several millimeters of lead are needed to stop gamma rays. Half-Life The time required for half of the atoms in any given quantity of a radioactive isotope to decay is the half-life of that isotope. Each particular isotope has its own half-life. For example, the half-life of 238 U is 4.5 billion years. That is, in 4.5 billion years, half of the 238 U on Earth will have decayed into other elements. In another 4.5 billion years, half of the remaining 238 U will have decayed. One fourth of the original material will remain on Earth after 9 billion years. Home...
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- Winter '08