Study of Matter Compounds  Elmhurst College
Atoms Physical Properties Mixtures  Chemistry Department
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 Iodine, I

Iodine has the symbol I.

From the Greek word "iodes" meaning "violet" and discovered by Bernard Courtois in France in 1811 .

Atomic Number = 53, Atomic Mass = 126.9, 53 protons, 53 electrons, 64 neutrons.

Most common use:

- iodide, and thyroxin which contains iodine, are used internally in medicine.
- A solution of KI and iodine in alcohol is used as a disinfectant for external wounds.
-silver iodide is used in photography
- added to table salt for nutrition to stop goiter in the thyroid
- deep blue color in a starch solution is a sign of the free element


Physical Properties:


Iodine is a solid diatomic non-metal that is very pungent in odor and a corrosive poison.
Th density of iodine is 4.94 g/mL, which means it will sink in water.


Chemical Properties:

Iodine, I2 is not reactive towards with oxygen, O2, or nitrogen, N2.

Iodine, I2, reacts with water to produce hypoiodite, OI-. The position of the equilibrium depends very much upon the pH of the solution.

In the graphic on the left, iodine element reacts with zinc metal to form zinc iodide. The reaction is so exothermic that part of the iodine element solid is vaporized to iodine violet gas.