Artificial radioisotopes

Thirty isotopes are recognized. Only one stable isotope, 1271 is found in nature. The artificial radioisotope 1311, with a half-life of 8 days, has been used in treating the thyroid gland. The most common compounds are the iodides of sodium and potassium (KI) and the iodates (KIOs). Lack of iodine is the cause of goiter. 

Sodium is not found ia the free state ia nature because of its high chemical reactivity. It occurs naturally as a component of many complex minerals and of such simple ones as sodium chloride, sodium carbonate, sodium sulfate, sodium borate, and sodium nitrate. Soluble sodium salts are found ia seawater, mineral spriags, and salt lakes. Principal U.S. commercial deposits of sodium salts are the Great Salt Lake Seades Lake and the rock salt beds of the Gulf Coast, Virginia, New York, and Michigan (see Chemicals frombrine). Sodium-23 is the only naturally occurring isotope. The six artificial radioisotopes (qv) are Hsted ia Table 1 (see Sodium compounds). 

Radioisotope—An unstable or radioactive isotope of an element that decays or disintegrates spontaneously, emitting radiation. Approximately 5,000 natural and artificial radioisotopes have been identified. 

Both naturally occurring and artificial radioisotopes find application in medicine, industrial products, and consumer products. Some specific radioisotopes, called fall-out, are still found in the environment as a result of nuclear weapons use or testing. 

ISOTOPES There are 30 isotopes of manganese, ranging from Mn-44 to Mn-69, with only one being stable Mn-55 makes up 100% of the element in the Earth s crust. All the other isotopes are artificially radioactive with half-lives ranging from 70 nanoseconds to 3.7x10 years. Artificial radioisotopes are produced in nuclear reactors, and because most radioactive isotopes are not natural, they do not contribute to the elemenfs natural existence on Earth. 

The isotope iodine-131 is an artificial radioisotope of iodine used as a tracer in biomedical research and as a treatment for thyroid disease. 1-131 has a half-hfe of about eight days, which means it will be eliminated from the body in several weeks. 

A small dose of a soluble fast-decay positron-emitting artificial radioisotope (produced as needed not too far from the PET instrument 6C11, 8015, 9F18 or 37Rb82) is put into human tissue (e.g., blood) the positron typically travels about 1 mm, meets an electron from within the human body, and the pair decays into two y photons of energy 0.51 MeV each, within microseconds to nanoseconds. Two spin states are possible for the positron— electron ion pair before their annihilation singlet and triplet. The annihilation rate for the triplet state depends sensitively on the electron density of the body tissue. Two y counters are set in coincidence mode, and several hundred thousand coincidence events are used to provide valuable tissue information (in addition to a CT scan). 

Radiation sources are treated in the above bibliography. One book deals exclusively with this subject a section is devoted to health hazards and protection from radiation. Two types of source are available, those from natural or artificial radioisotopes produced in nuclear reactors and those from a particle accelerator. The first includes nuclear recoil processes which are used for studying hot atom displacement reactions in the gas phase. 

CAS 7439-96-5. Mn. Metallic element of atomic number 25, group VIIB of periodic table, aw 64.9380, valences = 2, 3, 4, 6, 7 no stable isotopes four artificial radioisotopes. 

Mauchline, J. (1980) Artificial radioisotopes in the marginal seas of north western Europe. In The North-west European Shelf Sea the Sea Bed and the Sea in Motion. II. Physical and Chemical Oceanography and Physical Resources, eds. F.T. Banner, M.B. Collins and K.S. Massie, 517-42. Elsevier. Amsterdam. 

Santschi, P. H. (1988), Factors Controlling the Biogeochemical Cycles of Trace Elements in Fresh and Coastal Marine Waters as Revealed by Artificial Radioisotopes, Limnol. Oceanogr. 33, 848-866. 

In 1919, Lord Rutherford made the first artificial radioisotope by bombarding nitrogen atoms with alpha particles ... 

The first artificial radioisotope to be produced was made by Irene Curie and Joliot in 1934. The reaction again involved the use of energetic a-particles, colliding this time with boron, B. The product of the reaction, an isotope of nitrogen, decayed by emission of a positive electron or positron, thus ... 

A wide variety of reactions are now utilised for the production of artificial radioisotopes. Some examples are ... 

Thallium has two naturally occurring isotopes — Tl and Tl — yet it has 28 artificial radioisotopes, with half-lives ranging from 3.78 years to 0.2 seconds. 

Isotope dilution mass spectrometry (ID-MS) is widely accepted as a quantification procedure of proven accuracy in elemental analysis and isotope ratio measurements [4]. Several areas of research in nuclear science, geochronology, medicinal chemistry, environmental science, and agricultural science have benefited from this technique. ID-MS is applicable to all elements that have at least two stable isotopes. Monoisotopic elements can be analyzed only if they have a long-lived natural or artificial radioisotope. For example, iodine and thorium have been determined with spikes of the long-lived isotopes 29i and 25 Th, respectively [44]. TI-MS and ICP-MS are the methods of choice for accurate ID-MS analysis. ICP-MS has the advantage that several elements can be analyzed simnltaneously under the same experimental conditions. Other ionization techniqnes discussed in this chapter have also been coupled with ID-MS. 

Nuclear synthesis became feasible after invention of the cyclotron and the discoveries of neutrons and artificial radioactivity. In early thirties a few artificial radioisotopes of known elements were synthesized. Syntheses of heavier-than-uranium elements were even reported. But physicists just did not dare to take the challenge of the empty boxes at the very heart of the periodic system. It was explained by a variety of reasons but the major one was enormous technical complexity of nuclear synthesis. A chance helped. At the end of 1936 the young Italian physicist E. Segre went for a post-graduate work at Berkley (USA) where one of the first cyclotrons in the world was successfully put into operation. A small component was instrumental in cyclotron operation. It directed a beam of charged accelerated particles to a target. Absorption of a part of the beam led to intense heating of the component so that it had to be made from a refractory material, for instance, molybdenum. 

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