Actinium, determination

Lin [ 1 ] used coprecipitation with lead sulfate to separate 237-actinium from sea water samples. The 237-actinium was purified by extraction with HDEHP, and determined by alpha spectrometry via Si (Au) surface barrier detection. The method has a sensitivity of 10 3 pCig"1 of ashed sample. 

Francium - the atomic number is 87 and the chemical symbol is Fr. The name derives from the country France , where the French physicist Marguerite Percy from the Curie Institute in Paris, France discovered it in 1939 in the alpha particle decay of actinium, Ac => He => Fr, which was known as actinium-K and has a half-life of 22 minutes. An earlier claim of discovery in 1930 with the element name Virginium was determined to be incorrect. A similar claim for discovery of the element with atomic number 87 and named moldavium was also determined to be incorrect. The longest half-life associated with this unstable element is 22 minute Fr. 

Percival DR, Martin DB. 1974. Sequential determination of radium-226, radium-228, actinium-227, and thorium isotopes in environmental and process waste samples. Anal Chem 46 1742-1749. 

Elements 43, Masurium 61, Illinium 84, Polonium or Radium F 89, Actinium 91, Uranium Xs do not appear in the atomic weight tables. Although their existence has been indicated by means of X-rays or radioactive properties, they have not been isolated in amounts to allow of atomic weight determination. 

The formation constants of an actinium isopropyltropolonate complex were determined. Thermochemically relevant studies of thorium enolates generally involve bis(pentamethyl-cyclopentadienyl)thorium derivatives. Cp 2Th(Cl)(C(0)CFl2Bu-f) with an anionic acyl group that readily rearranges to the isomeric enolate Cp 2Th(Cl)OCH=CHBu-t. The Z-isomer is formed upon heating and the -isomer upon catalysis with Cp 2ThH2. Is the E or Z enolate thermodynamically more stable For the simple alkyl enolates MeCH=CHOR, the equilibration reaction of the Z- and E-isomers is nearly thermo-neutral . Consider the two species Cp 2Th(H)OCH(Bu-t)2 and Cp 2Th(H)0-2,6-C6H3 (Bu-f)2. The reversible addition of CO yields the rp- formyl derivative in reactions that are 19 4 and 25 6 kJmoR exothermic. These formyl species dimerize to form the classical enediolate, Cp 2Th(OR)OCH=CHO(OR)ThCp 2. This product is formed as the Z-isomer, plausibly thermodynamically preferred over the -isomer, much as (Z)-MeOCH=CHOMe is preferred over its E-counterpart by 6.0 0.2 kJmoR. ... 

In natural U, the radionuclides of the uranium family and the actinium family are present, and sometimes also radionuclides of the thorium family. Therefore, direct determination of U in ores without chemical separation is difficult, especially since the absorption of the radiation depends on the nature of the minerals. Generally, the samples are dissolved and Th is separated, e.g. by coprecipitation or by extraction with thenoyltrifluoroacetone (TTA). Radioactive equilibrium between " Th and the daughter nuclide 234mp jg rather quickly attained, and the high-energy yS" radiation of the latter can easily be measured. A prerequisite of the determination of U by measuring the activity of either " Th or 234mp jg establishment of radioactive equilibrium. This means that the uranium compound must not have been treated chemically for about 8 months. 

In the case of Th, the attainment of radioactive equilibrium with the daughter nuclides is very slow, because of the long half-life of Ra (q/2 = 5.75 y). Th can be determined directly by measuring its a radiation, but the measurement of Po is more sensitive (about 10 g Th can be determined in this way in 1 g of rock material). Other methods are based on the separation and measurement of Ra or Rn. In all determinations of Th, the possibility of the presence of radioactive impurities, mainly of members of the uranium and actinium families, has to be taken into account. 

Thirty-four isotopes of actinium are known, all of which are radioactive. The isotope that occurs in nature is actinium-227. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element s name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope. A radioactive isotope is one that breaks apart and gives off some form of radiation. 

Actinium-217 decays by releasing an alpha particle. Write an equation for this decay process, and determine what element is formed. 

Radon was discovered in 1899 by the McGill University professors Ernest Rutherford and Robert Owens, who found that radioactive thorium produced radioactive gas. They named this gaseous substance thorium emanation, later to become thoron. It was found that radium gave off a similar emanation (radon), as did actinium (actinon), in 1900 and 1904, respectively. Once the structure of the atom and the elemental transmutation process became better understood, it was determined that thoron, radon, and actinon were different isotopes of the same element (radon)— °Rn, Rn, and Rn, respectively. 

When an element has more than one radioisotope, determinations and data analysis are generally more complex because the isotopes may differ in half-life, especially when a series is involved, e.g., radium, thorium, polonium, radon, actinium, protactinium, and uranium. One possibility is to make measurements after the decay of the short-lived radionuclides, but this may require long waiting times. In favorable cases, it is more convenient to measure the activity of decay products (e.g., radon, thoron ( Rn), actinon ( Rn)), or correct the measurements of the short-lived radioisotopes after determination of the isotopic composition. 

Emanometric methods are radioanalytical methods that use measurement of radioactive isotopes of inert gases for the determination of appropriate elements. A good example is the use of the radon isotopes Rn, Rn, and Rn to determine radon, thorium, radium, and actinium. Indirect determinations... 

The kind of analysis outlined above can yield accurate assessments of the extent to which f electrons participate in the chemical bonding in the lighter actinides, but they are dependent upon accurate experimental data for actinium and the transplutonium elements. Both thermochemical and optical spectroscopic data are also useful for analysis of the factors determining the oxidation states of the actinide atom in compounds (Johansson 1977a, Brooks et al. 1984). For example, the stability of 450 different halides and oxides of the lanthanides were investigated, and the existence or non-existence of di-, tri- and tetravalent compounds was accounted for very well (Johansson 1977a). 

Friedrich Ernst Dom in 1900. He used the same apparatus as Rutherford with thorium emanation and confirmed this. Using radium bromide he found a similar emanation, which did not penetrate aluminium as Rutherford (incorrectly) said thorium emanation did. Some doubts about the existence of radium emanation were removed by Rutherford and Soddy, who liquefied it by cooling in liquid air, and by Ramsay and Collie, who determined its spectrum. R. W. Gray and Ramsay determined its density by weighing on a microbalance and proposed for it the name m/on, shining . Actinium emanation was discovered by Debieme and by Giesel. The modem names thoron, radon, and actinon were proposed by W. Schmidt. ... 

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