What Are the Causes of Helium Atom Disintegration?
Helium atom disintegration is the stochastic (random), spontaneous breakdown of a radioactive atom's unstable nucleus, or "radioactive decay." It is impossible to predict atom by atom, but decay rate can be predicted using the Law of Large Numbers, as researchers report at Carleton College. Only isotopes of an element can undergo decay because they have unstable inner nuclei that are prone to releasing energy.
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Unstable Nuclei
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Isotopes are radioactive forms of atoms with unstable nuclei. The nucleus of each atom breaks down to form more stable, non-radioactive atoms. During breakdown, energy is released by the emission of alpha, beta or gamma particles. Large isotopic nuclei can produce all three. Alpha particle disintegration is the loss of one alpha particle from an atomic nuclei -- which is equivalent to the nucleus of a helium atom having only two protons and two neutrons.
High Energy
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Unstable isotopes readily break down. It is as if they have too much energy and need to release it. This follows a common principle seen elsewhere in physics -- the second law of thermodynamics. Objects become less energetic over time unless they are forcibly given new energy. As energy is released, the parent radionuclide transforms into a lower energy daughter nuclide. The daughter is usually a different chemical element -- because part of its structure has changed.
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Cosmic Bombardment
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A continually-occurring, natural cause of radioactive isotopes -- and therefore isotopic disintegration -- is the cosmic ray bombardment of material in the Earth's crust or atmosphere. Radioisotopes produced this way are called "cosmogenic radionuclides." Without cosmic bombardment, there would be fewer radioactive isotopes present to undergo decay. Although creation of the parent radionuclide is only an indirect reason for decay, it is an important point to make. Carbon-14 is a well-known example of a cosmogenic isotope, according to the University of Arizona.
Chance
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Because helium atom disintegration is spontaneous, it occurs mostly by chance. This means that it is a process defined by the laws of probability. Only decay of the nuclei of large groups of atoms can be predicted with accuracy. The process is mathematically random, rather than simply chaotic, which means there are ways to compute the possibilities. This is why scientists use radioactive decay to date substances too old to identify using other means.
Artificial Creation
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Radioisotopes can be made at high speeds in expensive nuclear reactors, particle accelerators or radionuclide generators. Typical products include thalium-201 and iridium-192. Neutron capture is an example of a regularly used method of artificial creation, as explained by scientists at the University of Wisconsin. Artificially-produced isotopes are particularly useful in chemistry and medicine because they can help identify atoms from different sources when applied as a "tracer" or label.
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