Iodine Atomic number 53 Atomic weight 126 9045

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Iodine Atomic number 53 Atomic weight 126. 9045

History • Iodine was discovered by Bernard Courtois in 1811, and since 1815 Gay Lyussak began to consider it as a chemical element.

Structure and bonding • Iodine normally exists as a diatomic molecule with a I-I bond length of 270 pm, one of the longest single bonds known. The I 2 molecules tend to interact via the weak van der Waals force called the London Forces, and this interaction is responsible for the higher melting point compared to more compact halogens, which are also diatomic. Since the atomic size of Iodine is larger, its melting point is higher. The solid crystallizes as orthorhombic crystals.

Stay in the nature • Iodine is an element rare. His Clark of only 400 mg/t. But iodine has one feature — extreme absent-mindedness in the nature. Being far not the most widespread element, iodine is present practically everywhere. Is in a type of iodides in sea water (20 — 30 mg on ton of sea water). Is present at live organisms, most of all in algas (5 kg on ton of the dried-up sea cabbage (laminaria).

Physical properties • Iodine under usual conditions — firm black-gray substance with metal shine and a specific smell. Steams have characteristic violet color, the same as also solutions in unpolar organic solvents, for example in benzene — unlike a brown solution in polar spirit. Iodine at room temperature represents dark-violet crystals with weak shine. At heating at atmospheric pressure it sublimated, turning to steams of violet color; at pair cooling of iodine be crystallized, passing a liquid state. It use in practice for clearing iodine from nonvolatile impurity. • Melting point 114 °C • Boiling point 184 °C

Chemical properties With metals iodine at easy heating vigorously cooperates, forming iodides: Hg + I 2 = Hg. I 2 With hydrogen iodine reacts only when heating and not completely, forming chlorine iodine: I 2 + H 2 = 2 HI

Application in medicine • 5 -percent spirit solution of iodine is used for skin disinfection round damage, but not for intake at deficiency of iodine in an organism. It is widely advertized in alternative (informal) medicine, however its use without appointment of the doctor is generally a little proved and is quite often accompanied by various advertizing statements.

Application in equipment • Laser thermonuclear synthesis. Some iodine-organic connections are applied to production of super-power gas lasers on the raised atoms of iodine (research in the field of laser thermonuclear synthesis and the industry). • Radio-electronic industry In recent years demand for iodine sharply raised from producers of liquid crystal displays.

Toxicity • Iodine is very poisonous. Lethal dose of 3 g. Causes defeat of kidneys and cardiovascular system. At steam inhalation of iodine there is a headache, cough, cold, can be swelled lungs. At hit on a mucous membrane of eyes there is a dacryagogue, eye pain and reddening.

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