Overview+of+Nuclear+Chemistry


 * =**Background information about Nuclear Chemistry**= Page prepared by Mr. Ted Hall

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Material directly from: __Encyclopedia of Physics__ and __Facts on File__ =Radioactivity= The term radioactivity refers to the decay of an unstable nucleus, the parent nucleus, to a daughter nucleus with concomitant radiation in the form of the emission of one or more particles.Among the various types of radioactivity, five are common enough to have been given special names:=alpha decay= This is a form of radioactivity, whereby an atomic nucleus spontaneously emits a helium nucleus, also called an alpha particle, and thus transmutes into a daughter nucleus having atomic number less by two and atomic mass less by four than those of the parent nucleus. Among the various types of radiation from radioactivity, the helium nuclei produced by alpha decay are relatively weakly penetrating due to their large mass while relatively highly ionizing due to their electric charge. An example of alpha decay is the spontaneous decay of Uranium 238 (atomic number 92, atomic mass 238) to Thorium-234 (atomic number 90, atomic mass 234):where the emitted alpha particle (with atomic number 2 and atomic mass 4) is a helium nucleus. Alpha decay is governed by the strong interaction. The process of alpha decay involves the tunneling of an alpha particle from inside the nucleus to outside.=beta decay= This is a form of radioactivity, whereby an atomic nucleus spontaneously emits an electron, also called a beta particle, and an antineutrino of electron type, thus transmuting into a daughter nucleus with the same atomic mass as that of the parent nucleus and an atomic number greater by one. The basic process of beta decay is the conversion of a neutron within the nucleus to a proton, which remains inside the nucleus, and an electron and an antineutrino, which leave:where the symbols denote, from left to right, neutron, proton, electron, and electron-type antineutrino. This process is governed by the weak interaction. An example of beta decay is the decay of the radioactive isotope carbon-14, (atomic number 6, atomic mass 14)—used to determine the age of archaeological objects—to the stable isotope nitrogen-14,(atomic number 7, atomic mass 14):The energy difference between the parent and daughter nuclei emerges as the total energy of the emitted electron and antineutrino. That energy can be apportioned differently between the electron and the antineutrino in any individual decay process. So the electrons emitted by the radioactive decay of a sample of carbon-14, for example, will possess a range of energies not exceeding the carbon-14 to nitrogen-14 energy difference. In each individual decay, the antineutrino will carry the remainder of the energy difference not taken by the electron. The penetrating power of the electrons emitted by beta decay is strongly dependent on their energy. ||
 * =inverse beta decay= This is when a proton in a nucleus spontaneously converts to a neutron (which remains in the nucleus) and a positron and electron-type neutrino, which are emitted as follows:[[image:http://www.fofweb.com/Electronic_Images/ImageGallery/EQ-EnPhysBetaDecay2.jpg align="center" caption="external image EQ-EnPhysBetaDecay2.jpg"]]where e+ and //v//e denote the positron and the electron-type neutrino, respectively. An example of inverse beta decay is the decay of the radioactive isotope nitrogen-13, (atomic number 7, atomic mass 13), to the stable isotope carbon-13, (atomic number 6, atomic mass 13):[[image:http://www.fofweb.com/Electronic_Images/ImageGallery/EQ-EnPhysBetaDecay3.jpg align="center" caption="external image EQ-EnPhysBetaDecay3.jpg"]]Whereas free neutrons, not confined to a nucleus, undergo beta decay, free protons cannot undergo inverse beta decay. That is because the mass of the neutron is greater than that of the proton, so no energy is available for the decay. Within a nucleus, on the other hand, there might be available energy.=electron capture= **1.** The formation of a negative ion as a result of the capture of an electron by an atom or molecule or the formation of an atom or molecule by the capture of an electron by a positive ion.**2.** The transformation of a proton into a neutron in a nucleus by the capture of an inner orbital electron of the atom. A neutrino is emitted in this process. The emission of an X-ray photon is also associated with this process as a result of an outer electron falling into the vacancy created by the capture of the inner electron. The wavelength of the emitted photon is characteristic of the daughter element.=gamma decay= Gamma decay is a type of radioactivity in which a nucleus does not alter its identity, but rather makes a transition from a higher to a lower energy state while emitting a photon, also called a gamma ray. Gamma decay is governed by the electromagnetic interaction. Among the various types of radiation from radioactivity, the photons produced by gamma decay are the most strongly penetrating. Gamma decay can accompany alpha decay and beta decay when the latter leave the daughter nucleus in an excited state. Alpha decay of the radioactive isotope bismuth-212, to the isotope thallium-208, for example, can leave the latter in an excited state, from which it decays to its ground state by the emission of a photon.The name of this type of decay is a relic from the early years of the study of radioactivity.[[image:nuclearchem:gamma_decay.gif caption="gamma_decay.gif"]]

Radioactive Isotopes
Many isotopes, whether naturally occurring or artificially produced through nuclear reactions, are radioactive. All nuclei of atomic number greater than 83 are unstable and thus radioactive. The half-lives of the various radioactive isotopes range widely, from the exceptionally short, about 10–16 second, to as long as around 1021 years, which is much longer than the currently generally accepted value for the age of the universe (approximately 15 billion years, give or take a few billion).Bibliography:Angelo, Joseph A. "radioactivity." Encyclopedia of Space Exploration. New York: Facts On File, Inc., 2000. Facts On File, Inc. Science Online. .

Rennie, Richard. "nuclear reaction." The Facts On File Dictionary of Atomic and Nuclear Physics. Facts On File, Inc., 2003. Facts On File, Inc. Science Online. < www.fofweb.com >. Rosen, Joe. "Radioactivity." Encyclopedia of Physics. New York: Facts On File, Inc., 2004. Facts On File, Inc. Science Online. .

Rosen, Joe. "Alpha Decay." Encyclopedia of Physics. New York: Facts On File, Inc., 2004. Facts On File, Inc. Science Online. .

Rosen, Joe. "Beta Decay." Encyclopedia of Physics. New York: Facts On File, Inc., 2004. Facts On File, Inc. Science Online. .

Rosen, Joe. "gamma decay." Encyclopedia of Physics. New York: Facts On File, Inc., 2004. Facts On File, Inc. Science Online. .

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