Solid element 117 should be metallic in appearance, as is astatine, but it is expected that, instead of the −1 oxidation state characteristic of the natural halogens, it will show +1 and +3 oxidation states.
Element 117 is a member of the halogen series, which is the group composed of fluorine, chlorine, bromine, iodine, and astatine.
Naturally occurring astatine isotopes have subsequently been found in minute amounts in the three natural radioactive decay series, in which they occur by minor branching (astatine-218 in the uranium series, astatine-216 in the thorium series, and astatine-215 and astatine-219 in the actinium series).
However, the rarity of astatine means that these solutions are extremely dilute, with concentrations around or below 10−10 molarity (the number of moles per litre of solution).
The rare elements polonium and astatine are also sometimes included.
Astatine is usually prepared according to the general equation: which indicates that bismuth-209 takes up one alpha particle and emits x neutrons to form an isotope of astatine, whose atomic weight depends on the number of neutrons lost.
Astatine in the +1 state is stabilized by complexation, and complexes formulated as dipyridine astatine perchlorate [At(py)2] [ClO4] and dipyridine astatine nitrate [At(py)2] [NO3] have been prepared.
Continuing his research, he and his associates discovered the element astatine in 1940, and later, with another group, he discovered the isotope plutonium-239, which he found to be fissionable, much like uranium-235.
The only practical way of obtaining astatine is by synthesizing it through nuclear reactions.
If an aqueous solution of astatine is desired, the element may be separated by washing with an appropriate aqueous solution.
