Astatine decay

The element exists as an intermediate in uranium and thorium minerals through their decay. There is no stable isotope. The longest-living isotope has a half-life of 8.3 hours. In the crust of the Earth, the total steady-state mass is estimated at a few tens of grams. Thus astatine is the rarest element (record ). A few atoms of this relative of iodine can be found in all uranium ore. It exhibits certain metallic properties. 

ISOTOPES All 41 isotopes of astatine are radioactive, with half-lives ranging from 125 nanoseconds to 8.1 hours. The isotope As-210, the most stable isotope with an 8.1-hour half-life, is used to determine the atomic weight of astatine. As-210 decays by alpha decay into bismuth-206 or by electron capture into polonium-210. 

Chemists of the early twentieth century tried to find the existence of element 85, which was given the name eka-iodine by Mendeleev in order to fill the space for the missing element in the periodic table. Astatine is the rarest of all elements on Earth and is found in only trace amounts. Less than one ounce of natural astatine exists on the Earth at any one time. There would be no astatine on Earth if it were not for the small amounts that are replenished by the radioactive decay process of uranium ore. Astatine produced by this uranium radioactive decay process soon decays, so there is no long-term build up of astatine on Earth. The isotopes of astatine have very short half-lives, and less than a gram has ever been produced for laboratory study. 

Decay, Half-Lives, and Production of Astatine Isotopes"... 

All astatine isotopes, with the exception of At, produce other radionuclides by their decay, consequently complicated decay curves can arise. In astatine isotopes, electron capture (EC) always produces -radiation, h. Hours min, minutes s, seconds. 

Astatine-211 (ti/2 = 7.21 hours) possesses many of the desired physical (Fig. 5), chemical, and radiobiological properties thought pertinent to its possible application in cancer therapy (26,33,34,36,40). Astatine-211 decays along two branches (1) by direct a-particle decay (41.94 + 0.50% 5.87 MeV) to (tj/j = 38 years), which decays by electron... 

Astatine, 6 207-223, 31 43-88 as astatate ion, 6 219-220 as astatide ion, properties of, 6 217-218 biochemical compounds of, 6 222 biochemical fate, 31 78 biological behavior, 6 222 31 77-78 biomedical applications, 31 79-83 therapeutic studies, 31 80-81 chemical properties of, 6 216 diatomic, 31 50 distallation, 31 47-48 elementary, 6 218-219 embryotoxicity, 31 78 extraction techniques, 31 47 identification, 31 49 in intermediate oxidation state, 6 219 iodide, 6 218-219 isotopes, 31 43-49 decay, 31 44 half-lives, 31 44 decay and half-lives of, 6 210 experimental methods for, 6 213-216 production and measurement of, 6 209-216... 

D. R. Corson, K. R. Mackenzie, and E. G. Segre prepare element 85 (astatine) by bombarding bismuth with helions. W. Minder and Hulubei and Cauchois independently give evidence for the existence of element 85 in the decay products of radon. 

Radon, the heaviest of the noble gases, has been much publicized in recent years because of a fear that low-level exposures increase the risk of cancer. Like astatine and francium, its neighbors in the periodic table, radon is a radioactive element with only a minute natural abundance. It is produced by radioactive decay of the radium present in small amounts in many granitic rocks, and it can slowly seep into basements, where it remains unless vented. If breathed into the lungs, it can cause radiation damage. 

Astatine-197, decay scheme, 260f Atomic-beam spectroscopy, schematic view, 360f Atomic-beam technique, 358-363... 

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. 

Iodine is obtained by oxidizing iodides from seawater or brines using Cl2, concentrated H2S04, Fe3+, or other oxidizing agents. Astatine is produced naturally by the radioactive decay of uranium or thorium. Production of At is also accomplished by bombarding Bi with alpha particles,... 

Several chlorine isotopes exist with mass numbers ranging between 32 and 40. The two stable isotopes are Cl and Cl with natural abundances of 75.77% and 24.23% respectively, while the others are radioactive. Bromine also has two stable isotopes, Br and Br, with natural abundances of 50.69% and 49.31% respectively, while the others are radioactive. Iodine has only one stable isotope, and numerous radioactive ones are known. Astatine is known only as its radioisotope see Radioactive Decay). 

Astatine-211 is a promising radionuclide for systemic therapy1 3 due to its decay properties with a half-life of 7.2 hours and an effective emission of one a-particle per decay. However, the weakness of the astatine-protein bond formed after direct astatination1 4 has so far limited its clinical use. To overcome these problems indirect labelling methods have been tried such as the use of ALsuccinimidyl-(trialkylstannyl) benzoate as an intermediate for the astatination of antibodies using conjugation procedures.5 8... 

All natural radioelements with atomic numbers Z = 84 to 89 and Z = 91 have been identified as decay products of U and Th, but the first isotope of astatine (from Greek unstable Z = 85) was obtained in 1940 by the nuclear reaction... 

Astatine is a member of the halogen family, elements in Group 17 (VlIA) of the periodic table. It is one of the rarest elements in the universe. Scientists believe that no more than 25 grams exist on Earth s surface. All isotopes of astatine are radioactive and decay into other elements. For this reason, the element s properties are difficult to study. What is known is that it has properties similar to those of the other halogens—fluorine, chlorine, bromine, and iodine. Because it is so rare, it has essentially... 

Astatine is produced in Earth s cmst when the radioactive elements uranium and thorium decay. It can be made artificially only with great difficulty. By one estimate, no more than a millionth of a gram of astatine has ever been produced in the lab. 

Write the nuclear equation for the alpha decay of astatine-213. 

The last element of the group of metalloids is astatine. It has been estimated that the whole Earth s crust contains less than 44 mg astatine and this element with the atomic number 85 can thus be considered one of the rarest naturally occurring elements on Earth. All isotopes of this radioactive element have short half-lives and are products of several radioactive decay series. At (ti/2 = 54 s) occurs in one rare side branch of the decay series while At, one of the products of a side branch of the Po decay series, undergoes a very fast P decay (ti/2 = IxlO s). 

Not much is known about astatine because it is very rare, is radioactive, and decays very quickly. Would you predict the chemical and physical properties of astatine to be more... 

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