Isotopes of Astatine
|Isotope||Atomic Mass||Half-life||Mode of Decay||Nuclear Spin|
|At-207||206.98578||1.81 hours||EC to Po-207; α to Bi-203||9/2|
|At-208||207.98657||1.63 hours||EC to Po-208; α to Bi-204||6|
|At-209||208.98616||5.40 hours||EC to Po-209; α to Bi-205||6|
|At-210||209.987126||8.10 hours||EC to Po-210; α to Bi-206||5|
|At-211||210.98748||7.21 hours||EC to Po-211; α to Bi-207||9/2|
Astatine was discovered in 1940 by Dale R. Corson, Kenneth Ross MacKenzie and Emilio Segrè. Its name originates with the Greek word astatos, meaning "unstable."
Physical properties of this element have not been well investigated, due to the short half-lives of its isotopes. Astatine is volatile and may be distilled in a vacuum at room temperature in a glass apparatus; it may be condensed in a dry ice trap. It is soluble in chloroform, ether, hexane and many other organic solvents. Solubility in water should be of low order. Reactions of astatine should be similar to that of iodine; however, there is no evidence of existence of the diatomic molecule At2. Several compounds or polyanions are known. No practical uses of this element are known thus far.
Exposure to radiation may cause cancer. Studies on experimental animals show that such exposure induces tumors.
Properties of Astatine
|Standard state||Solid at 298 °K|
|CAS Registry ID||7440-68-8|
|Group in periodic table||17|
|Period in periodic table||6|
|Block in periodic table||p-block|
|Melting point||302 °C|
|Boiling point||230 °C|
|Thermal conductivity||1.7 (estimate) W/(m·K)|
|Heat of vaporization||About 40 kJ·mol-1|
|Heat of fusion||About 6 (per mole astatine atoms) kJ·mol-1|
|Density of solid||6.4 (estimated) g/cm3|
|Oxidation states in aqueous solution||-1, 0, +5, +7|
|Most stable isotope||At-210|