Forum Technical Discussions      Re: how mass is reduced as isotope decays? Posted by: N.Kuppusamy (PID_1818), E-mail: Address, on October 06, 2008 at 07:20 : In Reply to: Re: how mass is reduced as isotope decays? posted by : N.Kuppusamy , E-mail: Address, on October 06, 2008 at 06:50 : HI, There is a mistake. Please correct it as follows: There is a correction here. After one half-life the mass does not decayed to half of its original value. Only the activity is reduced by half. The mass is reduced in different proportion depnding on the type of decay. For example if an atom with mass no.8 emits alpha particle, it will reduce its mass by half after one half-life. While Uranium 238 which is alpha emitter reduduced its mass by 4 units by changing into daughter nucleus of Th-234. That is, 238 gram of Uranium 238 (1mole) changed in to 119 gram of Uranium 238 (1/2 mole) and 117 gram of Thorium 234 (1/2 mole). The remaing mass after 1 half life is therfore 119+117=236 grams and 2 grams (1/2 mole) of Helium emitted as alpha particles. 1mole of U238 = 238 gram (initial) ; After 1 half life, 1/2 mole of U238 = 119 gram 1/2 mole of Th234 = 117 gram 1/2 mole of He4 = 2 gram _____________________________ Total = 238 gram (after 1 half life) _____________________________ Regards, nks ----------- Start Original Message ----------- : Hi, : There is a correction here. After one half-life the mass does not decayed to half of its original value. Only the activity is reduced by half. : The mass is reduced in different proportion depnding on the type of decay. : For example if an atom with mass no.8 emits alpha particle, it will reduce its mass by half after one half-life. : While Uranium 238 which is alpha emitter reduduced its mass by 4 units by changing into daughter nucleus of Th-234. That is, 238 gram of Uranium 238 (1mole) changed in to 119 gram of Uranium 238 (1/2 mole) and 115 gram of Thorium 234 (1/2 mole). The remaing mass after 1 half life is therfore 119+115=234 grams and 4 grams (1mole) of Helium emitted as alpha particles. : Regards, : nks : : : Hi, : : : How the mass of an isotope like Ir-192 is reduced as the isotope decays? : : I fear that the various answer may have served to confuse further. : : After the half life of an isotope the mass of that isotope present will have decayed to half of its original value. : : However as an isotope decays it is converted into one or more new elements, having a total mass almost exactly the same. The only overall mass loss will be the weight of alpha particles (Helium nuclei, relatively heavy approx 4 AM units) beta particles (electrons, approx 0.0005 units) and the mass equivalent of emitted energy. In practice this is likely to be a negligible amount, of the order of parts per million or less, so no measurable overall mass loss will be observed . ------------ End Original Message ------------ Follow Ups: Hey Hey ! thargaity 12:41 Nov-28-2008 (0) Post a Followup: Name: E-Mail: Subject: Comments: ----------- Start Original Message ----------- : HI, : There is a mistake. Please correct it as follows: : There is a correction here. After one half-life the mass does not decayed to half of its original value. Only the activity is reduced by half. : The mass is reduced in different proportion depnding on the type of decay. : For example if an atom with mass no.8 emits alpha particle, it will reduce its mass by half after one half-life. : While Uranium 238 which is alpha emitter reduduced its mass by 4 units by changing into daughter nucleus of Th-234. That is, 238 gram of Uranium 238 (1mole) changed in to 119 gram of Uranium 238 (1/2 mole) and 117 gram of Thorium 234 (1/2 mole). The remaing mass after 1 half life is therfore 119+117=236 grams and 2 grams (1/2 mole) of Helium emitted as alpha particles. : 1mole of U238 = 238 gram (initial) ; After 1 half life, : 1/2 mole of U238 = 119 gram : 1/2 mole of Th234 = 117 gram : 1/2 mole of He4 = 2 gram : _____________________________ : Total = 238 gram (after 1 half life) : _____________________________ : Regards, : nks : : : Hi, : : There is a correction here. After one half-life the mass does not decayed to half of its original value. Only the activity is reduced by half. : : The mass is reduced in different proportion depnding on the type of decay. : : For example if an atom with mass no.8 emits alpha particle, it will reduce its mass by half after one half-life. : : While Uranium 238 which is alpha emitter reduduced its mass by 4 units by changing into daughter nucleus of Th-234. That is, 238 gram of Uranium 238 (1mole) changed in to 119 gram of Uranium 238 (1/2 mole) and 115 gram of Thorium 234 (1/2 mole). The remaing mass after 1 half life is therfore 119+115=234 grams and 4 grams (1mole) of Helium emitted as alpha particles. : : Regards, : : nks : : : : Hi, : : : : How the mass of an isotope like Ir-192 is reduced as the isotope decays? : : : I fear that the various answer may have served to confuse further. : : : After the half life of an isotope the mass of that isotope present will have decayed to half of its original value. : : : However as an isotope decays it is converted into one or more new elements, having a total mass almost exactly the same. The only overall mass loss will be the weight of alpha particles (Helium nuclei, relatively heavy approx 4 AM units) beta particles (electrons, approx 0.0005 units) and the mass equivalent of emitted energy. In practice this is likely to be a negligible amount, of the order of parts per million or less, so no measurable overall mass loss will be observed . ------------ End Original Message ------------ Optional Link URL: Example: "http://www....html". Alternative write "http://www.ndt.net/wshop/attach/filename.htm" if you transfered a filename.htm via FTP Page Title: is important! Optional Image URL: http://www....gif Attention! Please click the button only once. This may take a moment to process Forum Technical Discussions Help