Rubidium radioactive isotope

They produce distinctive colored flames when burned lithium = crimson sodium = yellow potassium = violet rubidium = purple cesium = blue and the color of francium s flame is not known. Many of francium s characteristics have not been determined owing to the fact that it is rare and all of its many radioactive isotopes have short half-lives. 

Potassium and sodium were first isolated within a few days of each other in 1807 by Humphry Davy as products of the electrolysis of molten KOH and NaOH. In 1817, J. A. Arfvedson, a young chemist working with J. J. Berzelius, recognized similarities between the solubilities of compounds of lithium and those of sodium and potassium. The following year, Davy also became the first to isolate lithium, this time by electrolysis of molten Li20. Cesium and rubidium were discovered with the help of the spectroscope in 1860 and 1861, respectively they were named after the colors of the most prominent emission lines (Latin, caesius, sky blue, rubidus, deep red). Francium was not identified until 1939 as a short-lived radioactive isotope from the nuclear decay of actinium. 

The radiochemical procedure for the determination of Cs in aqueous samples is based on the batch extraction of caesium onto a microcrystalline cation exchanger, ammonium molybdophosphate (AMP), and subsequent purification from potassium and rubidium activities by ion-exchange separation using a strongly acidic cation exchange resin (BIO-REX-40). Natural K and Rb have radioactive isotopes that interfere with the beta counting of Cs. The purification of caesium is also necessary to determine the chemical recovery. 

Rubidium is used to make atomic clocks. An atomic clock is a device for keeping very exact time. A radioactive isotope of rubidium is also used to measure the age of very old objects. In general, however, rubidium and its compounds have few practical uses. 

Rubidium-87 is a radioactive isotope. A radioactive isotope is one that breaks apart and gives off some form of radiation. Some radioactive isotopes occur naturally. Others can be produced artificially by firing very small particles at atoms. These particles stick in the atoms and make them radioactive. In addition to rubidium-87, 35 artificial radioactive isotopes of rubidium are also known. 

CAS 7440-17-7. Metallic element of atomic number 37, group IA of the periodic table, aw 85.4678, valence = 1. One stable form, principal natural radioactive isotope is rubidium-87. It is the second most electropositive and the second most alkaline element, has lowest ionization potential. Highly reactive. 

An unexpectedly high abundance of rubidium has been observed in asymptotic giant branch (AGB) stars with masses between about four and eight times that of the Sun. These stars are unusually active and exhibit thermal pulses that make for a high neutron density. Formation of the radioactive isotope 87Rb is, therefore, more likely than in cooler stars. Rubidium 87 has a half-life of 47 billion years, so once formed will remain with the star until the end of its life. Unfortunately, it has not been possible to measure the 87Rb content in stars. 

The radioactive isotope rubidium 82—another photon emitter—is also finding a useful niche in diagnostic medicine. As the tracer in PET (positron emission tomography) scans, rubidium is cheaper than the more commonly used ammonia, which must be produced in a particle accelerator. Combined with a CTscan that helps visualize blood flow, this method is currently the most accurate when imaging blood flow restrictions that may lead to cardiac arrest. 

A few salts of rubidium and cesium find application—for example the use of rubidium carbonate (Rb2C03) and cesium carbonate (Cs2C03) in the manufacture of glass and ceramics. Cesium fluoride (CsF) and cesium iodide (Csl) absorb X-rays and gamma rays and can be used in medical diagnostic equipment. In the form of cesium chloride (CsCl), the radioactive isotope cesium 137 is a source of gamma rays used in cancer treatment. In addition, cesium 137 is used in educational physics laboratory classes to study radioactivity. 

The trace alkali and alkaline earth cations are present in the following amounts lithium, 10-300 mg kg-1 rubidium, 20-500 mg kg-1 beryllium, 0.5-10 mg kg-1 strontium, 600-1000 mg kg-1 barium, 100-3000 mg kg-1 and radium, perhaps 10-7 mg kg-1. Some varieties of fmit trees are sensitive to as little as l mg L-1 Li+ in irrigation water, but Li+ toxicity is rare. Rubidium, cesium, strontium, and barium have all been studied in the laboratory, but have received little attention in the field. Strontium has been studied because its radioactive isotope 90Sr (half-life = 28 years) is produced by nuclear fission and could cause long-term soil contamination after nuclear explosions or accidents. In soils the toxic Be2+ ion behaves more like AI3 1 than like the other alkaline earth cations. 

In theory, diffusion coefficients can be measured for any ion. In practice, however, most studies of ionic diffusion in glasses have been restricted to highly mobile ions which have a convenient radioactive isotope for use in tracer measurements. As a result, a majority of the data for ionic diffusion deals with sodium, with lesser amounts of data for potassium, rubidium, and cesium. Studies of lithium are very limited due to the lack of a radioactive isotope of lithium, while studies of divalent and other, more highly charged, ions are restrieted by the very low mobilities of these ions as compared to those of the monovalent ions. 

This little story is mainly about my associations with potassium and rubidium, two elements in the alkali metal series of the periodic table. My Ph.D. thesis at the University of California in Berkeley (1934-1937) was concerned with potassium metabolism in the rat during pregnancy and lactation. In those days nutrition research was the major activity in biochemistry in the United States. In the course of my work I found among other things that the essential element, potassium, could be replaced by rubidium for growth of the rat, although after a time nervous disturbances and other toxic manifestations resulted. Rubidium is, in fact, transported by the same system which tissues use to take up potassium, so that nowadays one often measures potassium uptake activity with the radioactive isotope, Rb. The rubidium isotope happens to have a longer half-life and is more convenient to use than... 

ISOTOPES There are 30 isotopes of rubidium, ranging from Rb-75 to Rb-98. Rb-85 is the only stable form of rubidium and constitutes 72.17% of all rubidium isotopes found in the Earth s crust. Rb-87 is radioactive (a half-life of 4.9x10 ° years) and makes up about 27.83% of the remainder of rubidium found in the Earth s crust. All the other 28 isotopes make up a tiny fraction of all the rubidium found on Earth and are radioactive with very short half-lives. 

In the rubidium-strontium age dating method, radioactive 87Rb isotope with a natural isotope abundance of 27.85 % and a half-life of 4.8 x 1010 a is fundamental to the 3 decay to the isobar 87 Sr. The equation for the Rb-Sr method can be derived from Equation (8.9) ... 

When small amounts of isotopes are thus synthesized and must be separated from other chemical elements in a mixture, chemical periodicity helps for example, radioactive francium (group 1) can be extracted from its mixture with radium (group 2) or polonium (group 16) by adding cesium or rubidium (group 1). 

Whereas the abundance of Sr in rubidium rich rocks changes over time due to the radioactive 3 decay of Rb as a function of the primordial rubidium concentration and the age of the mineral, the abundance of the stable Sr isotope and consequently the Sr/ Sr is constant in nature. The constant Sr/ Sr isotope ratio is often used for internal standardization (mass bias correction) during strontium isotope ratio measurements of Sr/ Sr. In the rubidium-strontium age dating method, the isotope ratios Sr/ Sr and Rb/ Sr are measured mass spectrometrically (mainly by TIMS or nowadays by ICP-MS) and the primordial strontium ratio ( Sr/ Sr)o at t = 0 and the age t of the rock can be derived from the isochrone (graph of measured Sr/ Sr isotope ratios (represented on the ordinate) as a function of the Rb/ Sr ratio (on the abscissa) in several minerals with different primordial Rb concentrations). The age of the minerals will be determined from the slope of the isochrone (e — 1), and the primordial isotope ratio ( Sr/ Sr)o from the point of intersection with the ordinate (see Figure 8.9). Rb-Sr age dating is today an... 

Consider a rock that contains both rubidium and strontium. It will contain two isotopes of strontium. One is naturally occurring strontium-86, and the other is radioactive strontium-87, which is produced when the rock s rubidium-87 breaks down. 

Isochron age calculations are commonly made for the Rb-Sr (rubidium-strontium], Sm-Nd (samarium-neodymium], and U-Pb (uranium-lead] radioactive systems. They are most commonly applied to whole-rock systems, that is, a suite of samples thought to have formed at the same time, such as an igneous plu-ton or a suite of lavas. Isochron age calculations may also be made for a suite of minerals in a rock, in which case they date the time at which the minerals lost isotopic contact with each other, that is, became closed systems. This approach can be useful in dating metamorphism. 

With its predictable and unchanging rates, radioactive decay has provided scientists with a technique for determining the age of fossils, geological formations, and human artifacts. Using a knowledge of the half-life of a given radioisotope, one can estimate the age of an object in which the iso- tope is found. Four different isotopes are commonly used for dating objects carbon-14, uranium-238, rubidium-87, and potassium-40. Now look at one of these techniques in more detail. 

Chapter 4 examines the heavier alkali metals—rubidium, cesium, and francium. Francium is a radioactive, rare element its longest-lived isotope has a half-life of only 22 minutes. The relative abundances of rubidium and cesium are much less than the abundances of lithium, sodium, or potassium, yet rubidium and cesium find important applications in atomic clocks and laser technology. 

Strontium isotopes can be used to determine the ages of rocks. Radioactive rubidium 87 decays into strontium 87, with a half-life of 4.9 billion years. Geologists can use the ratio of Sr-87 to naturally occurring... 

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