At room temperature, iodine is solid and gray, but when heated, iodine changes directly from a gray solid to a violet-violet gas. Iodine is found mainly in seawater, algae, old brines and salt wells, as well as coastal sand and nitrate deposits. Iodine is formed in the same way as bromine; chlorine oxidizes the iodide (I-) ion present in algae to iodine (I) (McQuarrie, 2007). Silver iodide (AgI) and calcium diiodate (Ca(IO3)2) are the most common iodine minerals. Although pure iodine is toxic, elemental iodine is combined with potassium or sodium to create drugs and surgical antiseptics (Black, 2001). Silver iodide (AgI) is used in chemicals used in darkroom photography and cloud seeding, and iodine is added to table salt. Like fluorine and chlorine, iodine is essential to the human body. Iodine plays a key role in the functioning of thyroid hormones. Iodine deficiency will cause goiter, a thyroid deficiency disease characterized by swelling of the neck due to an enlarged thyroid gland. The thyroid gland enlarges to produce more iodine. This can be treated with potassium iodide (KI). Astatine was not presented in the Interchapter but is considered part of the halogen group. Astatine is a dark colored metallic solid. Astatine is highly radioactive and is produced synthetically by exploding bismuth (Bi) with alpha particles. It can be obtained naturally from the decay of thorium (Th) or uranium (U) (David, 2013). The most stable