Iodine

Halogen

Atomic Number: 53 • Atomic Mass: 126.9000 u • Period: 5 • Group: 17

Electron Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁵

Phase: Solid

Electronegativity: 2.66

History

Iodine has been known since ancient times

Discovered accidentally during production of saltpeter for gunpowder

Found in seaweed ash while extracting sodium and potassium compounds

Named for the violet vapor it produces when heated