Halogens, astatine

MF HF MIHFJ, M = Na,K [F—H... Fl [NiyiHCy, hydr. INRJlHBrJ, unstab. [NRJIHIJ 

Turova, Inorganic Chemistry in Tables, DOI 10.1007/978-3-642-20487-6 3, Springer-Verlag Berlin Heidelberg 2011 

chlorous ac., rapidly dec. in dil. s. HHCl + HCIO3 + CIO2) K = 10 , V. strong Ox 

X MCI+MCIO3, exp., angular [iCIOJ + M(Br03) , anion i/f-tetrah. 

K4H2I2O10 Ca2l209 - dimeso-KIO4 J, NaI04 - meta- 

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The elements of Group VHA are known as halogens (Greek, salt formers ). The term halides is used to describe their binary compounds. The heaviest halogen, astatine, is an artificially produced element of which only short-lived radioactive isotopes are known. 

In aqueous solution, astatine is usually found in the free (0) state. However, unlike the other halogens, astatine(O) is not diatomic. It can be volatilized from solution and extracted (like iodine) into organic solvents such as benzene and carbon tetrachloride. Coextraction with halogens, X2, into chloroform produces interhalogen compounds, AtX (X = Cl, Br, I). Reaction with halide ion, X , yields polyhalide ions, AtX2 (X = Br, I) and AtIBr , which can be extracted into isopropylether. 

The "time of flight" mass spectrometer has been used to confirm that this highly radioactive halogen behaves chemically very much like other halogens, particularly iodine. Astatine is said to be more metallic than iodine, and, like iodine, it probably accumulates in the thyroid gland. Workers at the Brookhaven National Laboratory have recently used reactive scattering in crossed molecular beams to identify and measure elementary reactions involving astatine. 

The Halogens Fluorine, Chlorine, Bromine, Iodine and Astatine... 

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