Radioactive decay is the set of various processes by which unstable atomic nucleus (nuclides) emit subatomic particles. Decay is said to occur in the ''parent nucleus'' and produce a ''daughter nucleus''. [[Image:radioactive.png|thumb|right|150px|The ''trefoil'' symbol is used to indicate radioactive material. The Unicode encoding of this symbol is U+2622 (☢).]] The SI unit for measuring radioactive decay is the becquerel (Bq). If a quantity of radioactive material produces one decay event per second, it has an activity of one Bq. Since any reasonably-sized sample of radioactive material contains very many atoms, a becquerel is a tiny level of activity; numbers on the order of gigabecquerels are seen more commonly. == General introduction == The neutrons and protons that constitute nuclei, as well as other particles that may approach them, are governed by several interactions. The strong nuclear force, not observed at the familiar macroscopic scale, is the most powerful force over subatomic distances. The electrostatic force is also significant. Of lesser importance are the weak nuclear force and the gravitational force. The interplay of these forces is very complex. Some configurations of the particles in a nucleus have the property that, should they shift ever so slightly, the particles could fall into a lower-energy arrangement. One might draw an analogy with a tower of sand: while friction between the sand grains can support the tower's weight, a disturbance will unleash the force of gravity and the tower will collapse. Such a collapse (a ''decay event'') requires a certain activation energy. In the case of the tower of sand, this energy must come from outside the system, in the form of a gentle prod or swift kick. In the case of an atomic nucleus, it is already present. Quantum mechanics particles are never at rest; they are in continuous random motion. Thus, if its constituent particles move in concert, the nucleus can ''spontaneously destabilize''. The resulting transformation changes the structure of the nucleus; thus it is a nuclear reaction, in contrast to chemical reactions, which concern interactions of electrons with nuclei. (Some nuclear reactions do involve external sources of energy, in the form of "collisions" with outside particles. However, these are not considered decay.) == Decay timing == As discussed above, the decay of an unstable nucleus (''radionuclide'') is entirely random and it is impossible to predict when a particular atom will decay. However, it is equally likely to decay at any time. Therefore, given a sample of a particular radioisotope, the number of decay events expected to occur in a small interval of time ''dt'' is proportional to the number of atoms present. If ''N'' is the number of atoms, the following first-order differential equation can be written: : Particular radionuclides decay at different rates, each having its own decay constant (lambda). The negative sign indicates that N decreases with each decay event. The solution to this equation is the following mathematical function: : This function represents exponential decay. It is only an approximate solution, for two reasons. Firstly, the exponential function is continuous, but the physical quantity ''N'' can only take positive integer values. Secondly, because it describes a random process, it is only statistically true. However, in most common cases, ''N'' is a very large number and the function is a good approximation. In addition to the decay constant, radioactive decay is sometimes characterized by the mean lifetime. Each atom "lives" for a finite amount of time before it decays, and the mean lifetime is the arithmetic mean of all the atoms' lifetimes. It is represented by the symbol tau, and is related to the decay constant as follows: : A more commonly used parameter is the half-life. Given a sample of a particular radionuclide, the half-life is the time taken for half the radionuclide's atoms to decay. The half life is related to the decay constant as follows: : This relationship between the half-life and the decay constant shows that highly radioactive substances are quickly spent, while those that radiate weakly endure longer. Half-lives of known radionuclides vary widely, from 1 E9 years for very nearly stable nuclides, to 1 E-6 seconds for highly unstable ones. == Modes of decay == Radionuclides can undergo a number of different reactions. These are summarized in the following table, in rough order of increasing rarity. For brevity, neutrons, protons and electrons are represented by the symbols ''n'', ''p+'', and ''e-'' respectively. {| !Name of reaction !! Participating particles !! Excitation of nucleus !! Change in atomic number |- |Alpha decay || Two ''n'' and two ''p+'' emitted from nucleus || Increases || Decreases by two |- |Beta decay || A ''n'' emits an ''e-'' and becomes a ''p+'' || Increases || Increases by one |- |Gamma decay || Excited nucleus releases a high-energy photon (gamma ray) || Decreases || No change |- |Positron emission || A ''p+'' emits a positron and becomes an ''n'' || Increases || Decreases by one |- |Internal conversion || Excited nucleus transfers energy to an electron orbital ''e-'' and ejects it || Decreases || No change |- |Proton emission || A ''p+'' ejected from nucleus || ? || Decreases by one |- |Neutron emission || A ''n'' ejected from nucleus || ? || No change |- |Electron capture || A ''p+'' combines with an orbiting ''e-'' and becomes an ''n'' || ? || Decreases by one |- |Spontaneous fission || Nucleus disintegrates into two or more smaller nuclei and other particles || ? || ? |} Radioactive decay results in a loss of mass, which is relativistic mass (the ''disintegration energy'') according to the formula . This energy is commonly released as photons (gamma radiation). == Decay chains and multiple modes == Many radionuclides have several different observed modes of decay. Bismuth-212, for example, has three. The daughter nuclide of a decay event is usually also unstable, sometimes even more unstable than the parent. If this is the case, it will proceed to decay again. A sequence of several decay events, producing in the end a stable nuclide, is a ''decay chain''. Of the commonly occurring forms of radioactive decay, the only one that changes the number of aggregate protons and neutrons (''nucleons'') contained in the nuclide is alpha emission, which reduces it by four. Thus, the number of nucleons modular arithmetic 4 is preserved across any decay chain. == Occurrence and applications == According to the Big Bang theory, radioactive isotopes of the lightest elements (hydrogen, helium, and traces of lithium) were produced very shortly after the emergence of the universe. However, these structures are so highly unstable that virtually none of these original nuclides remain today. With this exception, all unstable nuclides were formed in stars (particularly supernovae). Radioactive decay has been put to use in the technique of radioisotopic labelling, used to track the passage of a chemical substance through a complex system (such as a living organism). A sample of the substance is synthesized with a high concentration of unstable atoms. The presence of the substance in one or another part of the system is determined by detecting the locations of decay events. On the premise that radioactive decay is truly random (rather than merely chaos theory), it has been used in hardware random-number generators. == Related topics == * Nuclear physics * Poisson process * Radiation * Radioactive contamination == External links == * [http://www.epa.gov/radiation/understand/chain.htm Decay chains] * [http://www.atral.com/U2381.html Uranium-238 decay chain] * [http://www.ag.ohio-state.edu/~rer/rerhtml/rer_20.html Sulfur-38 decay chain] * [http://www.nuclides.net/Applets/about_radioactive_decay.htm List of decay modes] * [http://www.public.iastate.edu/~chemistry/Courses/chem178/apr23.html More examples] - does not work... * [http://www.nuclides.net/Nuclides_2000/U-232.htm Uranium-232 decay chain, Bismuth-212 decay modes] * [http://www.radiochemistry.org/nomenclature/i.htm Nomenclature of Radiochemistry] * [http://cadfael.cmc.sandia.gov/Central/public-docs/APrimeronRadiochemistry1.htm Radiochemistry Primer] - does not work... * [http://www2.slac.stanford.edu/vvc/theory/nuclearstability.html Nuclear stability] * [http://207.10.97.102/chemzone/lessons/11nuclear/nuclear.htm A page explaining nuclear decay] * [http://atom.kaeri.re.kr/ton/nuc2.html Table of Nuclides] Exponentials Radioactivity th:สารกัมมันตภาพรังสี
Perhaps this page can be folded into the Radioactivity page? It seems a bit redundant having both... ---- Both are usefull, this one on the mechanisms and pyhsics, the other one for the seconadry effects of decay, on environment, bioloy etc. Btw. does anyone know if there exists a formula by which, given the number of protons and neutrons, the half-life of a nucleus can be derived? :The best that I know is [http://atom.kaeri.re.kr/ton/nuc2.html Table of Nuclides], which I added to the article. I believe that these are all measured values, I don't think science can calculate these things accurately at present. User:Pstudier 22:55, 7 Oct 2004 (UTC) :If only nuclear physics were that advanced! Each of the decay mechanisms are very different processes with separate theoretical treatments. I think it's fair to say that most decay rates can be reproduced by theory to within an order of magnitude or thereabouts. All but the lightest nuclei represent extremely complex many-body problems that cannot be solved exactly (not at the moment anyway). You can make general comments, like for a particular isotope (i.e. constant proton number) the beta decay half-life gradually shortens as you move away from the line of stability (increasing or decreasing the number of neutrons). ::There is a formula that given A (total nuber of proton and neutron) and Z (number of proton) give you the approximate mass of the neuclide. But (in my opinion) is an empirical law (it has some parameter that are choose to make it better appriximate the empirical data). From this given a nuclide (A,Z) and a new neuclide (A*,Z*) you cnan know if the transform would be energetically favorible. But you have to take in account also the mass of the particle emitted. Unfourtunatelly it is not so easy, and this is not all of physics.User:AnyFile 11:38, 22 Nov 2004 (UTC) :Would someone be able to elaborate on the following: what makes a nuclide unstable? what accounts for differences in radionuclide decay constants? how does radioactive decay relate to the second law of thermodynamics? == Merge == The above argument for maintaining separate articles here and at Radioactivity is no longer valid. We need to decide which article will be kept, and which will be made into a redirect. The case as I see it is thus: * In favor of ''Radioactive decay'': More precise term. ''Radioactivity'' would then be turned into something between a stub and a disambig page, linking perhaps to Radiation, Radioactive decay, and Radioactive contamination. * In favor of ''Radioactive decay'': Leave redirect at ''Radioactivity''. User:Pstudier 23:00, 2004 Nov 14 (UTC) * In favor of ''Radioactivity'': More common term, more likely to be searched, easier to link to. *In favour. At the moment both page are not very scientific. Maybe also a rewriting or an extension are neededUser:AnyFile 11:40, 22 Nov 2004 (UTC) **Contesting your logic. I've been planning for weeks to rewrite this page, and I plan to proceed as soon as the merge takes place. It just seems foolish to start rewriting an article when I don't yet know what it will be entitled. ***May be I have express myself in a bad way. What I wanted to say is that there a lot of argument not covered and what is already written will need to be changed if I want to enlarge it.User:AnyFile 15:30, 24 Nov 2004 (UTC) --User:Smack 06:26, 23 Nov 2004 (UTC) Please add any new arguments to this list. --User:Smack 22:09, 14 Nov 2004 (UTC) ------ I can see no problem with keeping both. Wikipedia is not written on paper and data can be held several times over in different places with minimal extra cost. The principal search term will probably be ''Radioactivity'' but a more detailed look at ''Radioactive decay'', perhaps detailing the rate of decay of specific elements and isotopes would be very interesting and would be too much detail to hold on the Radioactivity article. User:Lumos3 09:43, 23 Nov 2004 (UTC) :While it is often useful to have some minor subtopics discussed in more than one article, it is generally accepted that it is impractical to keep multiple articles on essentially the same topic. Consolidating these two articles in one location will facilitate all manner of maintenance tasks and help prevent inconsistencies from arising. If you wish to continue this discussion further, please do so at Wikipedia talk:Duplicate articles, where it may garner input from Wikipedists more competent to address the issue. --User:Smack 18:18, 24 Nov 2004 (UTC) ------ == Question of naming == Let's have another vote. Should this article live here, or at Nuclear decay? The present title is favored by a Google test, seven to one. --User:Smack (User talk:Smack) 23:56, 24 Mar 2005 (UTC) *Those in favor of 'Radioactive decay': ** *Those in favor of 'Nuclear decay': **User:Smack (User talk:Smack) 23:55, 24 Mar 2005 (UTC) ** ==Types of radioactive decay== What determines which type of radioactive decay will happen? Thanks. --User:Eleassar777 12:09, 30 May 2005 (UTC) :It depends on many things like atomic weight, number of neutrons, number of protons, the relation of the previous values to each other and how much energy is "left over". --metta">User:Sunborn, The_Sunborn">User_talk:Sunborn 02:20, 31 May 2005 (UTC) Are there any (simple) equations that roughly describe this? How do these factors interact? Thanks. --User:Eleassar777 08:38, 31 May 2005 (UTC) :The decay mode that occurs is the one that releases the greatest amount of energy. As I understand it, if nucleus A can lose energy by emitting particle x, it will. (I'm not sure that this is true, but I don't see any reason why it wouldn't be.) If it can also lose energy by emitting particle y, it can go either way. I thought I'd made this clear in the article. Please tell me what's not clear, so that I can go and fix it. :I don't think there is an equation that predicts nuclear decays. Everything depends on the strong force, and physicists don't have a good model of that yet. AFAIK, the only analytical tool they have is nuclear binding energies. --User:Smack (User talk:Smack) 19:12, 31 May 2005 (UTC) ::Unfortunately things are not as simple as that. It depends on what the nucleus has too much of, protons or neutrons (this tells between beta and alpha decay), then how energetic the atom is (how much gamma emission). Random chance seems to have a large hand in things too. --metta">User:Sunborn, The_Sunborn">User_talk:Sunborn 22:20, 31 May 2005 (UTC) ::: No, no, things really are that simple. All of the considerations you mentioned are covered by the question of what transformation releases the greatest amount of energy. If a nucleus is tremendously proton-rich, it can lose a lot of energy by emitting a proton (and the same for neutrons). If it's in an excited state, it can lose energy by emitting a photon. --User:Smack (User talk:Smack) 04:57, 2 Jun 2005 (UTC) ==Emission of a Carbon 14 nucleus== One rare decay process that is not mentioned anywhere is the emission of a carbon-14 nucleus. I think it's like spontaneous fission, but acts like alpha decay in that the nucleus that is emitted always has the same mass number (14). Some isotopes of radium can decay by this method, such as Ra-221, Ra-222, Ra-223, Ra-224 and Ra-226. Reference: [http://education.jlab.org/itselemental/iso088.html Isotopes of Radium] -- B.d.mills ">User:B.d.mills (User talk:B.d.mills) 03:13, 15 Jun 2005 (UTC) :The reason they are not mentioned is that they occur so freaking rarely. But you are correct as far as I know. There are other rare decays not mentioned either. They include a Neon nucleus emission, a "double-beta" decay, and a triton decay. For instance the Ra-222, Ra-223, Ra-224 do a C-14 emission decay less than 0.001% of the time, the other two are much less than that. This is wikipedia, add the information if you can. I have much more important things to do, like make sure the actual articles on the elements have the correct data. You would be shocked by the wrong numbers. --metta">User:Sunborn, The_Sunborn">User_talk:Sunborn 03:39, 15 Jun 2005 (UTC) ::Neon emission, that's one I've not heard of before. Double-beta decay and double-electron capture are relatively common decay modes. They only ''happen'' rarely because they are only encountered as decay modes for long-lived isotopes like Calcium-48. I note them here for completeness. I don't plan to edit the articles because my current project is getting the articles for the constellations up to scratch. Good luck with your efforts to make the articles complete and accurate. -- B.d.mills ">User:B.d.mills (User talk:B.d.mills, Special:contributions/B.d.mills) 05:44, 22 Jun 2005 (UTC) Double electron capture is so rare most sources don't even say that it exists. My chart of the nuclides doesn't list it as a decay method, neither does [http://environmentalchemistry.com/yogi/periodic/ environmentalchemistry.com]. I have not heard of it other than here and will ask my professors when I get back to university. However, your quoted source does but it also lists the following types of emissions too: *Emission of an oxygen-20 nucleus (Th-228) *Emission of a neon nucleus (U-232) *Emission of a carbon-14 nucleus (Ac-225) *Emission of a magnesium-30 nucleus (U-236) *Emission of a silicon-34 nucleus (Cm-242) --metta">User:Sunborn, The_Sunborn">User_talk:Sunborn 15:05, 22 Jun 2005 (UTC) :Also, as per your request I started an article on all these particle decay emissions under the name, Cluster decay. I figure this is one of the terms used for this class decays. --metta">User:Sunborn, The_Sunborn">User_talk:Sunborn 19:20, 22 Jun 2005 (UTC) ::I made a minor error, I listed Calcium-48 as an isotope that decays by double elctron capture. It actually decays by double beta emission. For an isotope that decays by double electron capture, see Cadmium-106. [http://education.jlab.org/itselemental/iso048.html Isotopes of Cadmium] I get the impression that research into the decay of long-lived isotopes is relatively recent, because older texts still list these isotopes as stable. One test of these references is to inspect their entry for Bismuth. If they state that Bismuth-209 is stable then they may be unreliable sources for decay modes of long-lived isotopes. -- B.d.mills ">User:B.d.mills (User talk:B.d.mills, Special:contributions/B.d.mills) 02:15, 23 Jun 2005 (UTC)
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Radioactive decay
Radioactive decay is the set of various processes by which unstable atomic nucleus (nuclides) emit subatomic particles. Decay is said to occur in the ''parent nucleus'' and produce a ''daughter nucleus''. [[Image:radioactive.png|thumb|right|150px|The ''trefoil'' symbol is used to indicate radioactive material. The Unicode encoding of this symbol is U+2622 (☢).]] The SI unit for measuring radioactive decay is the becquerel (Bq). If a quantity of radioactive material produces one decay event per second, it has an activity of one Bq. Since any reasonably-sized sample of radioactive material contains very many atoms, a becquerel is a tiny level of activity; numbers on the order of gigabecquerels are seen more commonly. == General introduction == The neutrons and protons that constitute nuclei, as well as other particles that may approach them, are governed by several interactions. The strong nuclear force, not observed at the familiar macroscopic scale, is the most powerful force over subatomic distances. The electrostatic force is also significant. Of lesser importance are the weak nuclear force and the gravitational force. The interplay of these forces is very complex. Some configurations of the particles in a nucleus have the property that, should they shift ever so slightly, the particles could fall into a lower-energy arrangement. One might draw an analogy with a tower of sand: while friction between the sand grains can support the tower's weight, a disturbance will unleash the force of gravity and the tower will collapse. Such a collapse (a ''decay event'') requires a certain activation energy. In the case of the tower of sand, this energy must come from outside the system, in the form of a gentle prod or swift kick. In the case of an atomic nucleus, it is already present. Quantum mechanics particles are never at rest; they are in continuous random motion. Thus, if its constituent particles move in concert, the nucleus can ''spontaneously destabilize''. The resulting transformation changes the structure of the nucleus; thus it is a nuclear reaction, in contrast to chemical reactions, which concern interactions of electrons with nuclei. (Some nuclear reactions do involve external sources of energy, in the form of "collisions" with outside particles. However, these are not considered decay.) == Decay timing == As discussed above, the decay of an unstable nucleus (''radionuclide'') is entirely random and it is impossible to predict when a particular atom will decay. However, it is equally likely to decay at any time. Therefore, given a sample of a particular radioisotope, the number of decay events expected to occur in a small interval of time ''dt'' is proportional to the number of atoms present. If ''N'' is the number of atoms, the following first-order differential equation can be written: : Particular radionuclides decay at different rates, each having its own decay constant (lambda). The negative sign indicates that N decreases with each decay event. The solution to this equation is the following mathematical function: : This function represents exponential decay. It is only an approximate solution, for two reasons. Firstly, the exponential function is continuous, but the physical quantity ''N'' can only take positive integer values. Secondly, because it describes a random process, it is only statistically true. However, in most common cases, ''N'' is a very large number and the function is a good approximation. In addition to the decay constant, radioactive decay is sometimes characterized by the mean lifetime. Each atom "lives" for a finite amount of time before it decays, and the mean lifetime is the arithmetic mean of all the atoms' lifetimes. It is represented by the symbol tau, and is related to the decay constant as follows: : A more commonly used parameter is the half-life. Given a sample of a particular radionuclide, the half-life is the time taken for half the radionuclide's atoms to decay. The half life is related to the decay constant as follows: : This relationship between the half-life and the decay constant shows that highly radioactive substances are quickly spent, while those that radiate weakly endure longer. Half-lives of known radionuclides vary widely, from 1 E9 years for very nearly stable nuclides, to 1 E-6 seconds for highly unstable ones. == Modes of decay == Radionuclides can undergo a number of different reactions. These are summarized in the following table, in rough order of increasing rarity. For brevity, neutrons, protons and electrons are represented by the symbols ''n'', ''p+'', and ''e-'' respectively. {| !Name of reaction !! Participating particles !! Excitation of nucleus !! Change in atomic number |- |Alpha decay || Two ''n'' and two ''p+'' emitted from nucleus || Increases || Decreases by two |- |Beta decay || A ''n'' emits an ''e-'' and becomes a ''p+'' || Increases || Increases by one |- |Gamma decay || Excited nucleus releases a high-energy photon (gamma ray) || Decreases || No change |- |Positron emission || A ''p+'' emits a positron and becomes an ''n'' || Increases || Decreases by one |- |Internal conversion || Excited nucleus transfers energy to an electron orbital ''e-'' and ejects it || Decreases || No change |- |Proton emission || A ''p+'' ejected from nucleus || ? || Decreases by one |- |Neutron emission || A ''n'' ejected from nucleus || ? || No change |- |Electron capture || A ''p+'' combines with an orbiting ''e-'' and becomes an ''n'' || ? || Decreases by one |- |Spontaneous fission || Nucleus disintegrates into two or more smaller nuclei and other particles || ? || ? |} Radioactive decay results in a loss of mass, which is relativistic mass (the ''disintegration energy'') according to the formula . This energy is commonly released as photons (gamma radiation). == Decay chains and multiple modes == Many radionuclides have several different observed modes of decay. Bismuth-212, for example, has three. The daughter nuclide of a decay event is usually also unstable, sometimes even more unstable than the parent. If this is the case, it will proceed to decay again. A sequence of several decay events, producing in the end a stable nuclide, is a ''decay chain''. Of the commonly occurring forms of radioactive decay, the only one that changes the number of aggregate protons and neutrons (''nucleons'') contained in the nuclide is alpha emission, which reduces it by four. Thus, the number of nucleons modular arithmetic 4 is preserved across any decay chain. == Occurrence and applications == According to the Big Bang theory, radioactive isotopes of the lightest elements (hydrogen, helium, and traces of lithium) were produced very shortly after the emergence of the universe. However, these structures are so highly unstable that virtually none of these original nuclides remain today. With this exception, all unstable nuclides were formed in stars (particularly supernovae). Radioactive decay has been put to use in the technique of radioisotopic labelling, used to track the passage of a chemical substance through a complex system (such as a living organism). A sample of the substance is synthesized with a high concentration of unstable atoms. The presence of the substance in one or another part of the system is determined by detecting the locations of decay events. On the premise that radioactive decay is truly random (rather than merely chaos theory), it has been used in hardware random-number generators. == Related topics == * Nuclear physics * Poisson process * Radiation * Radioactive contamination == External links == * [http://www.epa.gov/radiation/understand/chain.htm Decay chains] * [http://www.atral.com/U2381.html Uranium-238 decay chain] * [http://www.ag.ohio-state.edu/~rer/rerhtml/rer_20.html Sulfur-38 decay chain] * [http://www.nuclides.net/Applets/about_radioactive_decay.htm List of decay modes] * [http://www.public.iastate.edu/~chemistry/Courses/chem178/apr23.html More examples] - does not work... * [http://www.nuclides.net/Nuclides_2000/U-232.htm Uranium-232 decay chain, Bismuth-212 decay modes] * [http://www.radiochemistry.org/nomenclature/i.htm Nomenclature of Radiochemistry] * [http://cadfael.cmc.sandia.gov/Central/public-docs/APrimeronRadiochemistry1.htm Radiochemistry Primer] - does not work... * [http://www2.slac.stanford.edu/vvc/theory/nuclearstability.html Nuclear stability] * [http://207.10.97.102/chemzone/lessons/11nuclear/nuclear.htm A page explaining nuclear decay] * [http://atom.kaeri.re.kr/ton/nuc2.html Table of Nuclides] Exponentials Radioactivity th:สารกัมมันตภาพรังสี
Radioactive decay
Perhaps this page can be folded into the Radioactivity page? It seems a bit redundant having both... ---- Both are usefull, this one on the mechanisms and pyhsics, the other one for the seconadry effects of decay, on environment, bioloy etc. Btw. does anyone know if there exists a formula by which, given the number of protons and neutrons, the half-life of a nucleus can be derived? :The best that I know is [http://atom.kaeri.re.kr/ton/nuc2.html Table of Nuclides], which I added to the article. I believe that these are all measured values, I don't think science can calculate these things accurately at present. User:Pstudier 22:55, 7 Oct 2004 (UTC) :If only nuclear physics were that advanced! Each of the decay mechanisms are very different processes with separate theoretical treatments. I think it's fair to say that most decay rates can be reproduced by theory to within an order of magnitude or thereabouts. All but the lightest nuclei represent extremely complex many-body problems that cannot be solved exactly (not at the moment anyway). You can make general comments, like for a particular isotope (i.e. constant proton number) the beta decay half-life gradually shortens as you move away from the line of stability (increasing or decreasing the number of neutrons). ::There is a formula that given A (total nuber of proton and neutron) and Z (number of proton) give you the approximate mass of the neuclide. But (in my opinion) is an empirical law (it has some parameter that are choose to make it better appriximate the empirical data). From this given a nuclide (A,Z) and a new neuclide (A*,Z*) you cnan know if the transform would be energetically favorible. But you have to take in account also the mass of the particle emitted. Unfourtunatelly it is not so easy, and this is not all of physics.User:AnyFile 11:38, 22 Nov 2004 (UTC) :Would someone be able to elaborate on the following: what makes a nuclide unstable? what accounts for differences in radionuclide decay constants? how does radioactive decay relate to the second law of thermodynamics? == Merge == The above argument for maintaining separate articles here and at Radioactivity is no longer valid. We need to decide which article will be kept, and which will be made into a redirect. The case as I see it is thus: * In favor of ''Radioactive decay'': More precise term. ''Radioactivity'' would then be turned into something between a stub and a disambig page, linking perhaps to Radiation, Radioactive decay, and Radioactive contamination. * In favor of ''Radioactive decay'': Leave redirect at ''Radioactivity''. User:Pstudier 23:00, 2004 Nov 14 (UTC) * In favor of ''Radioactivity'': More common term, more likely to be searched, easier to link to. *In favour. At the moment both page are not very scientific. Maybe also a rewriting or an extension are neededUser:AnyFile 11:40, 22 Nov 2004 (UTC) **Contesting your logic. I've been planning for weeks to rewrite this page, and I plan to proceed as soon as the merge takes place. It just seems foolish to start rewriting an article when I don't yet know what it will be entitled. ***May be I have express myself in a bad way. What I wanted to say is that there a lot of argument not covered and what is already written will need to be changed if I want to enlarge it.User:AnyFile 15:30, 24 Nov 2004 (UTC) --User:Smack 06:26, 23 Nov 2004 (UTC) Please add any new arguments to this list. --User:Smack 22:09, 14 Nov 2004 (UTC) ------ I can see no problem with keeping both. Wikipedia is not written on paper and data can be held several times over in different places with minimal extra cost. The principal search term will probably be ''Radioactivity'' but a more detailed look at ''Radioactive decay'', perhaps detailing the rate of decay of specific elements and isotopes would be very interesting and would be too much detail to hold on the Radioactivity article. User:Lumos3 09:43, 23 Nov 2004 (UTC) :While it is often useful to have some minor subtopics discussed in more than one article, it is generally accepted that it is impractical to keep multiple articles on essentially the same topic. Consolidating these two articles in one location will facilitate all manner of maintenance tasks and help prevent inconsistencies from arising. If you wish to continue this discussion further, please do so at Wikipedia talk:Duplicate articles, where it may garner input from Wikipedists more competent to address the issue. --User:Smack 18:18, 24 Nov 2004 (UTC) ------ == Question of naming == Let's have another vote. Should this article live here, or at Nuclear decay? The present title is favored by a Google test, seven to one. --User:Smack (User talk:Smack) 23:56, 24 Mar 2005 (UTC) *Those in favor of 'Radioactive decay': ** *Those in favor of 'Nuclear decay': **User:Smack (User talk:Smack) 23:55, 24 Mar 2005 (UTC) ** ==Types of radioactive decay== What determines which type of radioactive decay will happen? Thanks. --User:Eleassar777 12:09, 30 May 2005 (UTC) :It depends on many things like atomic weight, number of neutrons, number of protons, the relation of the previous values to each other and how much energy is "left over". --metta">User:Sunborn, The_Sunborn">User_talk:Sunborn 02:20, 31 May 2005 (UTC) Are there any (simple) equations that roughly describe this? How do these factors interact? Thanks. --User:Eleassar777 08:38, 31 May 2005 (UTC) :The decay mode that occurs is the one that releases the greatest amount of energy. As I understand it, if nucleus A can lose energy by emitting particle x, it will. (I'm not sure that this is true, but I don't see any reason why it wouldn't be.) If it can also lose energy by emitting particle y, it can go either way. I thought I'd made this clear in the article. Please tell me what's not clear, so that I can go and fix it. :I don't think there is an equation that predicts nuclear decays. Everything depends on the strong force, and physicists don't have a good model of that yet. AFAIK, the only analytical tool they have is nuclear binding energies. --User:Smack (User talk:Smack) 19:12, 31 May 2005 (UTC) ::Unfortunately things are not as simple as that. It depends on what the nucleus has too much of, protons or neutrons (this tells between beta and alpha decay), then how energetic the atom is (how much gamma emission). Random chance seems to have a large hand in things too. --metta">User:Sunborn, The_Sunborn">User_talk:Sunborn 22:20, 31 May 2005 (UTC) ::: No, no, things really are that simple. All of the considerations you mentioned are covered by the question of what transformation releases the greatest amount of energy. If a nucleus is tremendously proton-rich, it can lose a lot of energy by emitting a proton (and the same for neutrons). If it's in an excited state, it can lose energy by emitting a photon. --User:Smack (User talk:Smack) 04:57, 2 Jun 2005 (UTC) ==Emission of a Carbon 14 nucleus== One rare decay process that is not mentioned anywhere is the emission of a carbon-14 nucleus. I think it's like spontaneous fission, but acts like alpha decay in that the nucleus that is emitted always has the same mass number (14). Some isotopes of radium can decay by this method, such as Ra-221, Ra-222, Ra-223, Ra-224 and Ra-226. Reference: [http://education.jlab.org/itselemental/iso088.html Isotopes of Radium] -- B.d.mills ">User:B.d.mills (User talk:B.d.mills) 03:13, 15 Jun 2005 (UTC) :The reason they are not mentioned is that they occur so freaking rarely. But you are correct as far as I know. There are other rare decays not mentioned either. They include a Neon nucleus emission, a "double-beta" decay, and a triton decay. For instance the Ra-222, Ra-223, Ra-224 do a C-14 emission decay less than 0.001% of the time, the other two are much less than that. This is wikipedia, add the information if you can. I have much more important things to do, like make sure the actual articles on the elements have the correct data. You would be shocked by the wrong numbers. --metta">User:Sunborn, The_Sunborn">User_talk:Sunborn 03:39, 15 Jun 2005 (UTC) ::Neon emission, that's one I've not heard of before. Double-beta decay and double-electron capture are relatively common decay modes. They only ''happen'' rarely because they are only encountered as decay modes for long-lived isotopes like Calcium-48. I note them here for completeness. I don't plan to edit the articles because my current project is getting the articles for the constellations up to scratch. Good luck with your efforts to make the articles complete and accurate. -- B.d.mills ">User:B.d.mills (User talk:B.d.mills, Special:contributions/B.d.mills) 05:44, 22 Jun 2005 (UTC) Double electron capture is so rare most sources don't even say that it exists. My chart of the nuclides doesn't list it as a decay method, neither does [http://environmentalchemistry.com/yogi/periodic/ environmentalchemistry.com]. I have not heard of it other than here and will ask my professors when I get back to university. However, your quoted source does but it also lists the following types of emissions too: *Emission of an oxygen-20 nucleus (Th-228) *Emission of a neon nucleus (U-232) *Emission of a carbon-14 nucleus (Ac-225) *Emission of a magnesium-30 nucleus (U-236) *Emission of a silicon-34 nucleus (Cm-242) --metta">User:Sunborn, The_Sunborn">User_talk:Sunborn 15:05, 22 Jun 2005 (UTC) :Also, as per your request I started an article on all these particle decay emissions under the name, Cluster decay. I figure this is one of the terms used for this class decays. --metta">User:Sunborn, The_Sunborn">User_talk:Sunborn 19:20, 22 Jun 2005 (UTC) ::I made a minor error, I listed Calcium-48 as an isotope that decays by double elctron capture. It actually decays by double beta emission. For an isotope that decays by double electron capture, see Cadmium-106. [http://education.jlab.org/itselemental/iso048.html Isotopes of Cadmium] I get the impression that research into the decay of long-lived isotopes is relatively recent, because older texts still list these isotopes as stable. One test of these references is to inspect their entry for Bismuth. If they state that Bismuth-209 is stable then they may be unreliable sources for decay modes of long-lived isotopes. -- B.d.mills ">User:B.d.mills (User talk:B.d.mills, Special:contributions/B.d.mills) 02:15, 23 Jun 2005 (UTC)
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