Nuclear alpha decay

The alpha particle is a helium nucleus produced from the radioactive decay of heavy metals and some nuclear reactions. Alpha decay often occurs among nuclei that have a favorable neutron/proton ratio, but contain too many nucleons for stability. The alpha particle is a massive particle consisting of an assembly of two protons and two neutrons and a resultant charge of +2. 

Sometimes it is difficult to predict if a particular isotope is stable and, if unstable, what type of decay mode it might undergo. All isotopes that contain 84 or more protons are unstable. These unstable isotopes will undergo nuclear decay. For these large massive isotopes, we observe alpha decay most commonly. Alpha decay gets rid of four units of mass and two units of charge, thus helping to relieve the repulsive stress found in the nucleus of these isotopes. For other isotopes of atomic number less than 83, we can best predict stability by the use of the neutron to proton (n/p) ratio. 

Know that nuclear stability is best related to the neutron-to-proton ratio (n/p), which starts at about 1/1 for light isotopes and ends at about 1.5/1 for heavier isotopes with atomic numbers up to 83- All isotopes of atomic number greater than 84 are unstable and will commonly undergo alpha decay. Below atomic number 84, neutron-poor isotopes will probably undergo positron emission or electron capture, while neutron-rich isotopes will probably undergo beta emission. 

In the second of their 1915 papers (Harkins and Wilson 1915b), Harkins and Wilson note from their study of the light elements (up to atomic number 27) that the main isotopic species had atomic masses which are integral multiples of 4. They concluded from this that, for those light nuclei, an important constituent must be the alpha particle just as it must be in the heavier radioactive nuclei which undergo alpha decay. In order to rationalize all the nuclei, including their nuclear charges, they... 

The most important radioactive isotope of neptunium is Neptunium-237, with a half-life of 2.l44xl0+ years, or about 2.1 million years, and decays into protactinium-233 through alpha decay. Neptunium s most important use is in nuclear research and for instruments designed to detect neutrons. 

ORIGIN OF NAME Named after and in honor of the nuclear chemist Glenn T. Seaborg. ISOTOPES There a total of 16 Isotopes of unnilhexium (seaborgium) with half-lives ranging from 2.9 milliseconds to 22 seconds. All are artificially produced and radioactive, and they decay by spontaneous fission (SF) or alpha decay. 

Unnilseptium, or bohrium, is artificially produced one atom at a time in particle accelerators. In 1976 Russian scientists at the nuclear research laboratories at Dubna synthesized element 107, which was named unnilseptium by lUPAC. Only a few atoms of element 107 were produced by what is called the cold fusion process wherein atoms of one element are slammed into atoms of a different element and their masses combine to form atoms of a new heavier element. Researchers did this by bombarding bismuth-204 with heavy ions of chromium-54 in a cyclotron. The reaction follows Bi-209 + Cr-54 + neutrons = (fuse to form) Uns-262 + an alpha decay chain. 

Conservation of mass and charge are used when writing nuclear reactions. For example, let s consider what happens when uranium-238 undergoes alpha decay. Uranium-238 has 92 protons and 146 neutrons and is symbolized as After it emits an alpha particle, the nucleus now has a mass number of 234 and an atomic number of 90. 

Allotrope different forms of an element characterized by different structures Alloy a mixture of two or more metals, for example, zinc + copper = brass Alpha Decay nuclear process in which an alpha particle is emitted by the nucleus... 

Lumpkin, G. R. 2001. Alpha-decay damage and aqueous durability of actinide host phases in natural systems. Journal of Nuclear Materials, 289, 136-166. 

ALPHA DECAY. The emission of alpha particles by radioactive nuclei. The name alpha particle was applied in the earlier years of radioactivity investigations, before it was fully understood what alpha particles are. It is known now that alpha particles are the same as helium nuclei. When a radioactive nucleus emits an alpha particle, its atomic number decreases by Z = 2 and its mass number by A = 4. The process is a spontaneous nuclear reaction, and the radionuclide that undergoes the emission is known as an alpha emitter. 

Heyde, K. Basic Ideas and Concepts in Nuclear Physics, IOP, Bristol, 1994, pp. 82-103. Rrane, K. S. Introductory Nuclear Physics, Wiley, New York, 1988, pp. 246-271. Rasmussen, J. O. Alpha Decay, In K. Siegbahn (Ed.), Alpha-, Beta-, and Gamma-Ray Spectroscopy, North-Holland, Amsterdam, 1965, Chapter XI. 

The principle of small nuclear changes was given a theoretical basis by George Gamow. In 1928 he derived a successful theory of alpha decay, in which the nucleus is quantized and only small particles, such as protons or alpha particles, have a finite probability of tunneling through the nuclear barrier and escaping the nucleus. That... 

Alpha decay is nuclear decomposition such that one of the products of the reaction is an alpha (a) particle, 4He. In an example of alpha decay, radium-222 decomposes to form radon-218 plus an alpha particle ... 

O 029 Draw a chart in your notebook to show alpha decay, beta decay, gamma decay, nuclear fusion, and nuclear fission. Write a description and give an example of each type of reaction. Illustrate each example with a drawing. 

One prominent and well-known kind of nuclear component is that which is produced by the decay of naturally occurring radionuclides (see Table 1). The best- and longest-known examples are He, produced by alpha decay of the natural isotopes of uranium and Th, and " Ar, produced in one branch of the beta decay of " K. (There are several other natural radionuclides which produce He by alpha decay, but whether because of low parent abundance and/or very slow decay, only in very unusual samples is the production of He not strongly dominated by uranium and thorium.) Since radioactive decay laws are well known, the ratio of daughter to parent isotope(s) in a closed system is a simple function of time, whence this phenomenon has been long and extensively exploited as a geochronometer (e.g., see Chapter 1.16). 

Determine whether each of the following nuclear reactions involves alpha decay, beta decay, positron emission, or electron capture. 

Note also that a new element, radon (Rn), is created as a result of the alpha decay of the unstable radium-226 nucleus. The type of equation shown above is known as a nuclear equation because it shows the atomic number and mass number of the particles involved. It is important to note that both mass number and atomic number are conserved in nuclear equations. The accounting of atomic numbers and mass numbers below shows that they are conserved. 

Using the information provided in Table 25-3, write a balanced nuclear equation for the alpha decay of thorium-230 ( Th). 

Write the nuclear equation for the alpha decay of astatine-213. 

Write balanced nuclear equations for beta decay, positron emission, electron capture, and alpha decay processes and calculate the maximum kinetic energies of particles emitted (Section 19.2, Problems 7-18). 

The primary use for plutonium (Pu) is in nuclear power reactors, nuclear weapons, and radioisotopic thermoelectric generators (RTGs). Pu is formed as a by-product in nuclear reactors when uranium nuclei absorb neutrons. Most of this Pu is burned (fissioned) in place, but a significant fraction remains in the spent nuclear fuel. The primary plutonium isotope formed in reactors is the fissile Pu-239, which has a half-life of 24 400 years. In some nuclear programs (in Europe and Japan), Pu is recovered and blended with uranium (U) for reuse as a nuclear fuel. Since Pu and U are in oxide form, this blend is called mixed oxide or MOX fuel. Plutonium used in nuclear weapons ( weapons-grade ) is metallic in form and made up primarily (>92%) of fissile Pu-239. The alpha decay of Pu-238 (half-life = 86 years) provides a heat source in RTGs, which are long-lived batteries used in some spacecraft, cardiac pacemakers, and other applications. 

Alpha Decay. To achieve stable configurations, heavy elements, particularly those with atomic numbers above 70, may shed some of their nuclear mass by emitting a two-proton, two-neutron fragment identifiable after emission as a helium nucleus. Because nuclear radiations were observed before their identity was known, this fragment was called an alpha (a ) particle, and its emission is termed a-decay. Alpha particles are relatively large in mass, interact strongly with matter, but are absorbed by as little as a sheet of paper. However, because they are so heavy, even with low velocity. 

Once you know what kind of nucleus is produced by a simple nuclear reaction, you can determine what type of decay has taken place. If both the atomic number and mass number decrease, alpha decay has occurred. If the mass number stays the same but the atomic number increases, beta decay has occurred. If neither atomic number nor mass number changes, only gamma radiation has been emitted. 

When Fermi s group analyzed the products of the neutron bombardment, it appeared to them that radium had been produced, especially since they had no reason to even suspect that barium could be a product. Since radium is the daughter element formed by two successive alpha decays of a uranium atom, they decided their quest for a transuranium element was unsuccessful. Subsequently, Otto Hahn (1879-1968), Fritz Strassmann (1902-80), and Lise Meitner (1878-1968), all from Germany, reinterpreted the results to show that it was not radium atoms that had been formed, but barium atoms instead from the nuclear fission of uranium. Thus, Fermi and his group just missed discovering fission. 

Writing a Balanced Nuclear Equation Alpha Decay... 

Consider the decay of one isotope of uranium, 9 U, into thorium and an alpha particle. Because an alpha particle is lost in this process, this decay is called alpha decay. Examine the balanced equation for this nuclear reaction ... 

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