'Reuben+Foo'+Astatine+-+Rarest+Naturally+Occurring+Element

=__**Astatine**__= Astatine is a highly radioactive element with an atomic number of 85, represented on the periodic table by the symbol, At. It is currently the heaviest known halogen (Group VIIA elements). Astatine has a very short half life 1, therefore it only exists in minute amounts. In fact, astatine is currently the rarest naturally occuring element, with an estimated amount of less than 30 grams existing in the entire Earth's crust at any given time. This makes it extremely difficult to study this element, but the characterisitics of this element can be inferred from comparison to other elements.

Properties


Left column: Atomic Number, Melting Point, Boiling Point, Density (n.a). Center column: Electron Configuration, Name. Right column: Atomic Mass, Electronegativity, Symbol.

**Origin**
Astatine comes from the Greek word, //astatos//, meaning unstable.

**Production**
In nature, astatine is produced by the radioactive decay of uranium and thorium. Scientists have also managed to synthesise astatine by bombarding bismuth with alpha particles. However, this process is extremely difficult and only 0.05 micrograms of astatine has been produced to date.

Compounds
Astatine is expected to be able to form ionic bonds with metals, like other halogens. Astatine can also form covalent bonds with hydrogen, forming hydrogen astatide (HAt), a very strong acid.

**Isotopes**
This element currently has 33 isotopes, all of which are radioactive and very unstable. The longest living isotope, 210At, has a half life of 8.1 hours, while the shortest living isotope, 213At, has a half life of 125 nanoseconds.

**Uses**
Astatine is too rare to have any uses and are mainly used for scientific study. However, scientists have suggested a medical use for this element: radiation therapy. Astatine has close similarities to other halogens, especially iodine. One of them being its tendency to accumulate in the thyroid gland. Scientist hypothesise that this element can be used to cure certain diseases of the thyroid, such as hyperthyroidism 2 and thyroid cancer. When swallowed, the radiation it emits can kill off the cancer cells in the thyroid gland.

Definitions
1 The time it takes for a substance undergoing decay to reduce its quantity by half 2 A medical condition where the thyroid gland produces too much of the thyroid hormone

**Bibliography**
[] [| http://en.wikipedia.org/wiki/Astatine] [| http://education.jlab.org/itselemental/ele085.html] [| http://www.chemistryexplained.com/elements/A-C/Astatine.html]