Name Iodine
Symbol I
Atomic Number 53
Atomic Mass 126.90447 atomic mass units
Number of Protons 53
Number of Neutrons 74
Number of Electrons 53
Melting Point 113.5 C
Boiling Point 184.0 C
Density 4.93 grams per cubic centimeter
Normal Phase Solid
Family Halogens
Period 5
Cost $8.30 per 100 grams



Origin of Name From the Greek word iodes, meaning violet
Date and Place of Discovery In 1811 in France
Discovered by Barnard Courtois
Common Compounds
Interesting facts
  • Its the least reactive of the halogens.
  • Most living organisms require trace amounts of it in their diets.
  • Two-thirds of the iodine in a human body is found in the thyroid.
  • Iodine in the thyroid is the key to the metabolism, the ability to burn off calories.
  • Its vapor is very irritating to the eye.
  • It reacts with the alkali metals to form salts.
Common Uses
  • Internal treatment medications, especially thyroid problems like goiters
  • Food supplements
  • Photography
  • Water purification
  • Printing inks and dyes
  • Halogen lights
  • Catalysts
  • Animal feed


Photo Courtesy of
Cary Academy
Chemical Elements
Mrs. Purdy's Web Page

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