Protactinium-234, half-life

Each of the elements has a number of isotopes (2,4), all radioactive and some of which can be obtained in isotopicaHy pure form. More than 200 in number and mosdy synthetic in origin, they are produced by neutron or charged-particle induced transmutations (2,4). The known radioactive isotopes are distributed among the 15 elements approximately as follows actinium and thorium, 25 each protactinium, 20 uranium, neptunium, plutonium, americium, curium, californium, einsteinium, and fermium, 15 each herkelium, mendelevium, nobehum, and lawrencium, 10 each. There is frequently a need for values to be assigned for the atomic weights of the actinide elements. Any precise experimental work would require a value for the isotope or isotopic mixture being used, but where there is a purely formal demand for atomic weights, mass numbers that are chosen on the basis of half-life and availabiUty have customarily been used. A Hst of these is provided in Table 1. 

Merritt WR, Champion PJ, Hawkings RC (1957) The half-life of °Pb. Can J Phys 35 16 Pickett DA, Mnrrell MT, Williams R.W (1994) Determination of femtogram qnantities of protactinium in geological samples by thermal ionization mass spectrometry. Anal Chem 66 1044-1049 Robert J, Miranda CF, Mnxart R (1969) Mesure de la periode dn protactininm-231 par microcalorimetrie. Radiochim Acta 11 104-108... 

Meitnerium - the atomic number is 109 and the chemical symbol is Mt. The name derives from the Austrian physicist Lise Meitner , who had discovered the element, protactinium. The first synthesis of the element Meitnerium is credited to German physicists from the GSI (Center for Heavy-Ion Research) lab at Darmstadt, Germany under Gunther Miinzenberg, in 1982 using the nuclear reaction ° Bi ( Fe, n) Mt. The longest half-life associated with this unstable element is 0.07 second Mt. 

Protactinium is a relatively heavy, silvery-white metal that, when freshly cut, slowly oxidizes in air. AH the isotopes of protactinium and its compounds are extremely radioactive and poisonous. Proctatinium-231, the isotope with the longest half-life, is one of the scarcest and most expensive elements known. It is found in very small quantities as a decay product of uranium mixed with pitchblende, the ore of uranium. Protactiniums odd atomic number (gjPa) supports the observation that elements having odd atomic numbers are scarcer than those with even atomic numbers. 

It was first identified and named brevium, meaning brief, by Kasimir Fajans and O. H. Gohring in 1913 because of its extremely short half-life. In 1918 Otto Hahn (1879—1968) and Lise Meitner (1878-1968) independently discovered a new radioactive element that decayed from uranium into (actinium). Other researchers named it uranium X2. It was not until 1918 that researchers were able to identify independently more of the elements properties and declare it as the new element 91 that was then named protactinium. This is another case in which several researchers may have discovered the same element. Some references continue to give credit for protactinium s discovery to Frederich Soddy (1877—1956) and John A. Cranston (dates unknown), as well as to Hahn and Meitner. 

The most important radioactive isotope of neptunium is Neptunium-237, with a half-life of 2.l44xl0+ years, or about 2.1 million years, and decays into protactinium-233 through alpha decay. Neptunium s most important use is in nuclear research and for instruments designed to detect neutrons. 

PROTACTINIUM. [CAS 7440-13-13], Chemical element, symbol Pa, at. no. 91, at. wt, 231.036, radioactive metal of the Actinide Series, mp is estimated at less than 1600°C, All isotopes arc radioactive. The most stable isotope is 23IPa with a half-life of 3,43 v 104 years, The latter is a second-generation daughter of a5U and a member of the actinium (2n + 3) decay series, See also Radioactivity, Electronic configuration... 

Regelous et al have reported ou the use of the isotope dilutiou techuique (using a Pa spike with a half-life of 26.97 days) for the quantitative measurement of 20 fg of protactinium in silicate rocks after chemical separation of the actinide from the rock matrix by MC-ICP-MS (Neptune, Thermo Fisher Scientific, Bremen - equipped with uiue Faraday detectors, oue secondary electron multiplier and a retarding potential quadrupole for high abundance sensitivity measurements). 

The actinides are all radioactive elements. Actinium, thorium, protactinium, and uranium are the only four actinides that have been found in the environment the others are artificial, being produced through various nuclear reactions. It should be noted that at the creation of the universe some amount of Pu could have been formed however, with an 80 million year half-life, it would have fully decayed during the past 10 billion years. 

Analogous to the process releasing Ra to seawater, decay of Th in sediments releases dissolved Ra which is then mixed into the ocean interior. Radium-226 decays through a series of short-lived nuclides to Pb (half-life 22.3 yr) which, like thorium and protactinium, is insoluble and readily sorbs to particles. Radioactive decay of gaseous Rn in the atmosphere also produces Pb, which is then deposited on the sea surface with aerosols and in precipitation. Although Pb and, to a lesser extent, Pa have found many applications as tracers of particle transport, by far the greatest use has been made of thorium isotopes, which form the focus of this review. 

The half-life of protactinium-234 in its ground state is 6.69 h. What fraction of a given amount remains after 26.76 h ... 

Pa. The only isotope of protactinium with a half-life longer than 1 month is Pa. It is a member of the 4n + 3 decay series of U, occurring in secular equilibrium with natural uranium at a concentration about the same as that of radium. The activity of Pa in natural uranium at secular equilibrium is 0.022 Ci/Mg of uranium. 

An isotope of protactinium (having mass number 234 and a half-life of 1.1 minutes) was first identified by Kasimir Fajans and O. Gohring in 1913 as a short-lived member of the naturally occurring decay series and was given the name brevium, meaning brief The existence of protactinium was confirmed in 1918 when another isotope of protactinium (of mass 231 and a half-life of 3.3 X 10 years) was studied independendy by Otto Hahn and... 

A given type of radioactive nuclide always has the same half-life. However, the various radioactive nuclides have half-lives that cover a tremendous range. For example, jPa, protactinium-234, has a half-life of 1.2 minutes, and uranium-238, has a half-life of 4.5 x 10 (4.5 billion) years. This means that a sample containing 100 million Pa nuclei will have only 50 million nuclei in it (half of 100 million) after 1.2 minutes have passed. In another... 

The actinium decay series consists of a group of nuclides whose mass number divided by 4 leaves a remainder of 3 (the 4n + 3 series). This series begins with the uranium isotope which has a half-life of 7.04 X 10 y and a specific activity of 8 X 10 MBq/kg. The stable end product of the series is ° Pb, which is formed after 7 a- and 4 /3-decays. The actinium series includes the most important isotopes of the elements protactinium, actinium, ftancium, and astatine. Inasmuch as U is a conqx>nmt of natural uranium, these elem ts can be isolated in the processing of uranium minerals. The longest-lived protactinium isotope, Pa (ti 3.28 X 10 y) has been isolated on the 100 g scale, and is the main isotope for the study of protactinium chemistry. Ac (t 21.8 y) is the longest-lived actinium isotope. 

The process is plagued by both chemical and nuclear difficulties. The decay chain Th - forms 27 d half-life Pa. For a con >lete decay of all Pa to the spoit fuel elements must be cooled for about a year. A still considerable amount of longlived Pa is present in the spent fuel (about 1/2000 of the amount of U) protactinium complicates the reprocessing chemistry and constitutes an important waste hazard. 

Many transuranium elements, such as plutonium-232, have very short half-lives. (For Pu, the half-life is 36 minutes.) However, some, like protactinium-231 (half-life = 3.34 X 10 years), have relatively long half-lives. Use the masses given in the following table to calculate the change in energy when 1 mol Pu nuclei and 1 mol Pa nuclei are each formed from their respective number of protons and neutrons. 

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