Wikijunior:The Elements/Iodine

Shows the position of Iodine on the periodic chart.

Iodine's symbol on the Periodic Table

What does it look, feel, taste, or smell like?

Purple-pink iodine vapour in a flask.

Iodine is a dark grey or purple solid. It can sublimate into a purple-pink gas that has an irritating odor.

The solid iodine is a dark, almost black, grey or purple color.

How was it discovered?

Iodine was discovered by Barnard Courtois in 1811 by accident.

Where did its name come from?

Iodine gets its name from the Greek word iodes, which means purple. It is a purple element in both the solid and gas phase.

Where is it found?

Iodine is mostly found in seawater as iodide (I^-). Seaweed and kelp can absorb iodide and store it, making it easy to harvest.

Did You Know?

• Iodine changes directly from a solid to a gas at room temperature (this is called sublimation).
• Although many people think of iodine as a dark bluish liquid, it's actually a purple solid.

What are its uses?

Iodine is necessary as part of the diet of many organisms. This is because it is part of thyroid hormones produced by the thyroid gland in your neck. Not consuming enough iodine causes a condition called goiter, where the thyroid gland grows abnormally (so, ironically, does consuming too much iodine.) We "iodize" salt by putting iodine in it, converting some of the salt to sodium iodide (NaI), so that we can get the proper amount of iodine in our diet.

A solution of iodine is also used to kill bacteria when someone gets a cut.

Finally, iodine can be used to test for the presence of starch, because starch turns dark blue when it combines with iodine.

Is it dangerous?

Elemental iodine is dangerous and poisonous. Do not touch it.