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From the Greek "astatos," the name astatine reflects the nature of the heaviest halogen – it is an unstable, radioactive non-metal. Twenty isotopes are known, the longest having a half-life of eight hours. Because of its short half-life, this element has no commercial use.

Astatine's chemical properties resemble those of iodine, another halogen. It is believed that this element accumulates in the thyroid – like iodine. In fact, isotopes of astatine are occasionally preferred over radio-iodine in clinical use because the particles emitted from astatine isotopes provide more energy in combatting problems of hyperthyroidism and thyroid cancer. However, the use of astatine is limited because it also has a shown tendency to induce tumours.