Radium conversion

Although there are a number of isotopes of francium, most decay very rapidly to other elements. Most isotopes with masses of 223 AMU and lower emit tt-particles (consisting of two protons and two neutrons) to become astatine. Some low mass francium isotopes can also undergo electron capture (the conversion of a proton to a neutron through the absorption of an electron) to become radon. Francium isotopes with masses of 220 AMU and higher can undergo /3-decay (the conversion of a neutron to a proton through the emission of an electron) to become radium. Francium-223 is the most stable isotope and has a half-life of 21.8 minutes. 

In 1896 there came the discovery of radioactivity by Henri Becquerel and the discovery of radium by Pierre and Marie Curie. Soon thereafter it was recognized that radioactive changes involve the spontaneous conversion of atoms of one element into those of another. It then became necessary to change the definition of element this was done by saying that one element could not be converted into another by artificial means. 

More generally, arc lavas show excess, usually interpreted to be indicative of high U/Th solubility in aqueous fluids derived from subducting material. Ra excess is correlated with excess in most data sets on historically erupted lavas. Thus, if Ra excess is formed at great depth, it is likely (though not required see Thomas et al. (2002)) that excess is also formed at depth. Conversely, shallow processes that fractionate thorium from radium could also fractionate thorium from uranium. 

Radium is obtained from pitchblende, UgOg, in which it is formed by the disintegration of (p. 15), the equilibrium ratio being 3.4 x The sulphate is co-precipitated with BaS04 when BaClg is added to a sulphuric acid extract of the ore. After boiling with NaOH to remove lead, the sulphates are converted to carbonates by sodium carbonate fusion and dissolved in HCl to the chlorides. Fractional crystallisation of these removes much of the barium the final separation is effected by the same means after conversion to bromides. 

I o " dps. This niiniher was cho.sen for a hi.slorical la-son—this is the number of disintegrations per second in I g of radium. The intemalional sy.sieni of units has adoplni the becquerel as the official unit of radioactivity, but dr curie is still widely u.scd. and we will u.se this unit in addih ii to the official unit. A relevant conversion factor to lemctiibr is the following ... 

Evidence for the second viewpoint comes from measurements of longer-lived radionucleides within the radium decay sequence, specifically bismuth-210 and lead-210. The major routes for nuclei conversion within the radium decay scheme are shown in Fig. 7-27. The direct decay product of radium-226, an alpha-emitter, is radon-222, which escapes the Earth surface. Only the continents are a source the contribution from the oceans is negligible. Since the half-life time of radon-222 is only 3.8 days, its distribution in the troposphere is rather uneven. Over the continents the mixing ratio declines with increasing altitude (see Fig. 1-9). Over the oceans, the vertical gradient is reversed, as the oceans act as a sink and the zonal circulation keeps supplying material from the middle and upper troposphere. The immediate... 

Ans. The first artificial conversion of one nucleus to another was performed by E. Rutherford in 1919. He bombarded nitrogen-14 with a-particles emitted by radium and produced oxygen-17. The reaction is... 

In 1919, Ernest Rutherford performed the first conversion of one nucleus into another, using alpha particles emitted by radium to convert nitrogen-14 into oxygen-17 ... 

In 1938, Hahn, Strassman, and Meifner proved that they had fissioned the uranium atom using neutrons from an artificial source (a mixture of radium and beryllium). Scientists throughout the world used the values that were then known for the masses of the fission products versus that of the starting atom of uranium and concluded that a tremendous amount of energy is released in the fission process. The fissioning experiment was reproduced in about 100 different universities in the United States within the next year. The conversion of the mass lost in the fission process indicated that the fission of a uranium atom would release approximately 200 MeV (million electron volts). This is in sharp contrast to most chemical processes, such as combustion, which release only about 3-5 eV (electron volts) per combustion of a carbon or hydrogen atom. The ratio on an atom-to-atom basis is the order of 50,000,000 to 1. 

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