Elements radioactive

Radiochemical tracers, compounds labeled with radioisotopes (qv), have become one of the most powerful tools for detection and analysis in research, and to a limited extent in clinical diagnosis (see Medical IMAGING TECHNOLOGY). A molecule or chemical is labeled using a radioisotope either by substituting a radioactive atom for a corresponding stable atom in the compound, such as substituting for H, for or for P, and for for 

Radiometric detection technology offers high sensitivity and specificity for many appUcations in scientific research. The radioactive emission of the labeled compound is easily detected and does not suffer from interference from endogenous radioactivity in the sample. Because of this unique property, labeled compounds can be used as tracers to study the localization, movement, or transformation of molecules in complex experimental systems. 

The use of radioactive tracers was pioneered by Georg von Hevesy, a Hungarian physical chemist, who received the Nobel Prize in 1943 for his work on radioactive indicators (1). Radioisotopes have become indispensable components of most medical and life science research strategies, and in addition the technology is the basis for numerous industries focused on the production and detection of radioactive tracers. Thousands of radioactive tracers have been synthesized and are commercially available. These are used worldwide in tens of thousands of research laboratories. 

Any radioactive nucUde or isotope of an element can be used as a radioactive tracer, eg, chromium-51 [14392-02-0] cobalt-60 [10198-40-0] tin-110 [15700-33-1] and mercury-203 [13982-78-0],hut the preponderance ofuse has been for carbon-14 [14762-75-5],hydj ogen-3 [10028-17-8] (tritium), sulfur-35 [15117-53-0], phosphoms-32, and iodine-125 [14158-31 -7]. More recendy phosphoms-33 has become available and is used to replace sulfur-35 and phosphoms-32 in many appUcations. By far the greater number of radioactive tracers produced are based on carbon-14 and hydrogen-3 because carbon and hydrogen exist in a large majority of the known natural and synthetic chemical compounds. 

Isotope CAS Registry Number Half-hfe, Specific activity, Bq/mmol Eneigy, MeV, % Decay product 

Sometimes, the nucleus of an atom cam have extra neutrons. The normal atom and the one with extra neutrons have the same atomic numbers. This is because they have the same number of protons. They have different masses because of the extra neutrons. Scientists call these atoms isotopes. 

All elements have isotopes. Many isotopes occur naturally. Some occur by themselves, like sodium. Other elements in nature are actually mixtures of several isotopes. Oxygen that occurs 

Mass spectrometry determines the effects of drugs in the body, identifies illegal steroids in an athlete, and determines the age and origin of once-living material in archeology. 

Health and Medicine For diagnosis of heart disease, cancer, and for therapy. Every year more than 30 million medical treatments and over 100 million laboratory tests are completed using isotopes. 

Environment For the measurement of air and water pollution and to understand the effects of radioactive waste on the public and environment. 

The term radioactivity was coined by Marie Curie to describe the phenomenon of an atomic species constantly emitting penetrating radiation , that is, radiation capable of passing through matter and 

Although other components of penetrating radiation have since been discovered, the three listed, 

Understanding solids the science of materials. Richard J. D. Tilley 2004 John Wiley Sons, Ltd ISBNs 0 470 85275 5 (Hbk) 0 470 85276 3 (Pbk) 

Very soon after the radioactivity of thorium and uranium had been discovered it was found that pure samples of both of these elements were only very weakly radioactive. However, such pure samples became more and more radioactive with time until they reached a steady level identical to that in the original samples before pmification. This suggested that the uranium or thorium atoms were transforming or decaying into other radioactive daughter elements and that hitherto undiscovered series of such elements might exist. The search for the radioactive products of uranium by Marie and Pierre Curie led to the characterisation of two new elements, which were named polonium, Po, and radium, Ra. Both elements are far more radioactive than uranium and decay so rapidly that no ore deposits are formed. They exist only because they are formed constantly from naturally occurring uranium. 

Since that time, in the early years of the 20th century, many radioactive elements have been prepared, and radioactive forms of the majority of the elements in the periodic table are readily available 

---

Radioactive elements may often be prepared artificially by bombarding the atoms of ordinary stable elements with, e.g. helium nuclei. See radioactivity, artificial. 

The transformations of the radioactive elements, whereby, e.g. uranium ultimately becomes lead, are not usually regarded as instances of transmutation because the processes are spontaneous, and cannot be controlled by the experimenter. 

This is a radioactive element. It occurs in minute traces in barium and thorium minerals, but it can be produced by irradiation of bismuth in a nuclear reactor. (The study of its chemistry presents great difficulty because of its intense a radiation). 

There are many potential advantages to kinetic methods of analysis, perhaps the most important of which is the ability to use chemical reactions that are slow to reach equilibrium. In this chapter we examine three techniques that rely on measurements made while the analytical system is under kinetic rather than thermodynamic control chemical kinetic techniques, in which the rate of a chemical reaction is measured radiochemical techniques, in which a radioactive element s rate of nuclear decay is measured and flow injection analysis, in which the analyte is injected into a continuously flowing carrier stream, where its mixing and reaction with reagents in the stream are controlled by the kinetic processes of convection and diffusion. 

Neutron Activation Analysis Few samples of interest are naturally radioactive. For many elements, however, radioactivity may be induced by irradiating the sample with neutrons in a process called neutron activation analysis (NAA). The radioactive element formed by neutron activation decays to a stable isotope by emitting gamma rays and, if necessary, other nuclear particles. The rate of gamma-ray emission is proportional to the analyte s initial concentration in the sample. For example, when a sample containing nonradioactive 13AI is placed in a nuclear reactor and irradiated with neutrons, the following nuclear reaction results. 

Equations 13.31 and 13.32 are only valid if the radioactive element in the tracer has a half-life that is considerably longer than the time needed to conduct the analysis. If this is not the case, then the decrease in activity is due both to the effect of dilution and the natural decrease in the isotope s activity. Some common radioactive isotopes for use in isotope dilution are listed in Table 13.1. 

Radioactive Gemstones. Zircon can contain radioactive elements, but the amount in jewelry-grade material is insignificant. Some of the treatments of Table 3 may leave irradiated material radioactive. Such gemstones have been released on rare occasions without the required cooling-off period (10). 

Lead, atomic number 82, is a member of Group 14 (IVA) of the Periodic Table. Ordinary lead is bluish grey and is a mixture of isotopes of mass number 204 (15%), 206 (23.6%), 207 (22.6%), and 208 (52.3%). The average atomic weight of lead from different origins may vary as much as 0.04 units. The stable isotopes are products of decay of three naturally radioactive elements (see Radioactivity, natural) comes from the uranium series (see Uraniumand... 

See Immunoassay Medical diagnostic reagents Radioactive elements. 

Thorium [7440-29-1], a naturally occurring radioactive element, atomic number 90, atomic mass 232.0381, is the second element of the actinide ( f) series (see Actinides AND transactinides Radioisotopes). Discovered in 1828 in a Norwegian mineral, thorium was first isolated in its oxide form. For the light actinide elements in the first half of the. series, there is a small energy difference between and 5/ 6d7 electronic configurations. Atomic spectra... 

Uranium [7440-61-17 is a naturally occurring radioactive element with atomic number 92 and atomic mass 238.03. Uranium was discovered in a pitchblende [1317-75-5] specimen ia 1789 by M. H. Klaproth (1) who named the element uranit after the planet Uranus, which had been recendy discovered. For 50 years the material discovered by Klaproth was thought to be metallic uranium. Pnligot showed that the uranit discovered by Klaproth was really uranium dioxide [1344-57-6] UO2, and obtained the tme elemental uranium as a black powder in 1841 by reduction of UCl [10026-10-5] with potassium (2). 

In 1896, Becquerel discovered that uranium was radioactive (3). Becquerel was studying the duorescence behavior of potassium uranyl sulfate, and observed that a photographic plate had been darkened by exposure to the uranyl salt. Further investigation showed that all uranium minerals and metallic uranium behaved in this same manner, suggesting that this new radioactivity was a property of uranium itself In 1934, Fermi bombarded uranium with neutrons to produce new radioactive elements (4). 

Nuclear-physical methods ai e the basic ones in controlling environmental pollution which results from nucleai -power complexes and power plants work. Oil and gas production leads to the extraction of radio nuclides of natural origin in considerable amounts, which later spread from oil-slimes and water wastes in the neighborhoods of oil and gas producing entei prises. Similaidy, toxic and radioactive elements can pollute environment in case of mineral deposits extraction. 

Nuclear methods which include a variety of radioactive elements as in organic reagents, complexes or salts. 

Radon A radioactive element, the heaviest of the noble gases, formed by the radioactive decay of radium. 

Tlie kind of trcuisformation tliat will take place for any given radioactive element is a function of the type of nuclear instability as well as the mass/eiiergy relationship. Tlie nuclear instability is dependent on the ratio of neutrons to protons a different type of decay will occur to allow for a more stable daughter product. The mass/energy relationship stales tliat for any radioactive transformation(s) the laws of conservation of mass tuid tlie conservation of energy must be followed. 

An alplia p uticle is an energetic helium nucleus. The alplia particle is released from a radioactive element witli a neutron to proton ratio tliat is too low. The helium nucleus consists of two protons and two neutrons. The alplia particle differs from a helimn atom in that it is emitted witliout any electrons. The resulting daughter product from tliis tj pe of transformation lias an atomic number Uiat is two less tluin its parent and an atomic mass number tliat is four less. Below is an e. aiiiple of alpha decay using polonium (Po) polonium has an atomic mass number of 210 (protons and neutrons) and atomic number of 84. 

It is also necessary to explain the existence of naturally occurring radioactive elements whose half-lives (or those of their precursors) are substantially less than the presumed age of the universe. 

The related problem arising from radioactive elements is considered in the next section. 

The isolation and identification of 4 radioactive elements in minute amounts took place at the turn of the century, and in each case the insight provided by the periodic classification into the predicted chemical properties of these elements proved invaluable. Marie Curie identified polonium in 1898 and, later in the same year working with Pierre Curie, isolated radium. Actinium followed in 1899 (A. Debierne) and the heaviest noble gas, radon, in 1900 (F. E. Dorn). Details will be found in later chapters which also recount the discoveries made in the present century of protactinium (O. Hahn and Lise Meitner, 1917), hafnium (D. Coster and G. von Hevesey, 1923), rhenium (W. Noddack, Ida Tacke and O. Berg, 1925), technetium (C. Perrier and E. Segre, 1937), francium (Marguerite Percy, 1939) and promethium (J. A. Marinsky, L. E. Glendenin and C. D. Coryell, 1945). 

The fugitive radioactive element astatine can hardly be said to exist in nature though the punctillious would rightly point to its temporary participation in the natural radioactive series. Thus At (t i 54 s) occurs as a... 

---