I
Iodine
Atomic number: 53Mass: 126.904 uCategory: Halogen
About Iodine
Iodine is a non-metallic, lustrous, purple-black solid at room temperature. It sublimes to a beautiful violet gas when heated. It is an essential micronutrient — without enough iodine, the thyroid gland swells into a goitre.
Properties
Period
5
Group
17
Block
P
Category
Halogen
Electronegativity
2.66 (Pauling)
Ionization Energy
1008.4 kJ/mol
Melting Point
387 K (114°C)
Boiling Point
457 K (184°C)
Density
4.933 g/cm³
Oxidation States
-1, +1, +3, +5, +7
Electron Configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁵
[Kr] 4d¹⁰ 5s² 5p⁵
Shell 1:2e⁻
Shell 2:8e⁻
Shell 3:18e⁻
Shell 4:18e⁻
Shell 5:7e⁻
Real-World Uses
Antiseptic (iodine solution)
Thyroid medication
Radiography contrast
Photography
Water purification
Fun Fact
Iodine sublimates directly from solid to purple-violet gas without becoming liquid — it's used as a test for starch, turning deep blue-black on contact!