Astatine, atomic

On the basis of what you have learned about the physical and chemical properties and reactions of CI2/ Br2, and I2 and/or of HF, HCl, HBr, and HI, write an essay describing clearly what physical and chemical properties and reactions you would expect for elemental astatine (atomic number 85) and/or its acid, HAt (as designated by your instructor). 

Can you use data in Tabie 7.7 to provide estimates for the atomic radius and first ionization energy of an astatine atom ... 

Some striking regularities are evident, especially for the heavier elements. The elements of odd atomic number have only one or two natural nucleides, whereas those of even atomic number are much richer in nucleides, many having eight or more. It is also found that the odd elements are much rarer in nature than the even elements. The elements with no stable isotopes (technetium, atomic number 43 astatine, atomic number 85, promethium, atomic number 61) have odd atomic numbers. 

By considering the trends in the vertical groups of the Periodic Table, deduce possible answers to the following questions concerning the element astatine (At), atomic number 85. 

C09-0133. Among the halogens, only one known molecule has the formula X 7. It has pentagonal bipyramidal geometry, with five Y atoms in a pentagon around the central atom X. The other two Y atoms are in axial positions. Draw a ball-and-stick model of this compound. Based on electron-electron repulsion and atomic size, determine the identities of atoms X and Y. Explain your reasoning. (Astatine is not involved. This element is radioactive and highly unstable.)... 

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. 

M Astatine is isolated in tiny amounts from reactor materials. The Bohr atomic model shows the tightly packed electron shell. One can formally see" the instability. It was the last of the 92 naturally occurring elements to be found. 

A stage org chem) An early stage in a thermosetting resin reaction characterized by linear structure, solubility, and fusibility of the material. a, staj astatine chem A radioactive chemical element, symbol At, atomic number 85, the heaviest of the halogen elements. as-t3,ten asterism (spect) A star-shaped pattern sometimes seen in x-ray spectrophotographs. as-t3,riz-om ... 

Astatine - the atomic number is 85 and the chemical symbol is At. The name derives from the Greek astatos for unstable since it is an unstable element. It was first thought to have been discovered in nature in 1931 and was named alabamine. When it was determined that there are no stable nuclides of this element in nature, that claim was discarded. It was later shown that astatine had been synthesized by the physicists Dale R. Corson, K. R. Mackenzie and Emilio Segre at the University of California lab in Berkeley, California in 1940 who bombarded bismuth with alpha particles, in the reaction Bi ( He, 2n ) "At. Independently, a claim about finding some x-ray lines of astatine was the basis for claiming discovery of an element helvetium, which was made in Bern, Switzerland. However, the very short half-life precluded any chemical separation and identification. The longest half-life associated with this unstable element is 8.1 hour °At. 

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. 

Astatine is located just below iodine, which suggests that it should have some of the same chemical properties as iodine, even though it also acts more hke a metal or semimetal than does iodine. It is a fairly heavy element with an odd atomic number, which assisted chemists in learning more about this extremely rare element. The 41 isotopes are man-made in atomic reactors, and most exist for fractions of a second. The elements melting point is about 302°C, its boiling point is approximately 337°C, and its density is about 7g/cm. ... 

The halogens will be restricted to chlorine, bromine and iodine since fluorine, as the most electronegative element, does not function as the central atom in a complex and astatine has only short-lived, radioactive isotopes, so that very little of its coordination chemistry has been investigated.2 ... 

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

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