Discovery date : 1811
Discovered by: Bernard Courtois
Origin of the name: The name is derived from the Greek 'iodes' meaning violet.
Allotropes : I2
~>IODINE is a chemical element with symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a lustrous, purple-black metallic solid at standard conditions that sublimes readily to form a violet gas.
| FACT BOX | |||
| Group | 17 | Melting point | 113.7°C, 236.7°F, 386.9 K |
| Period | 5 | Boiling point | 184.4°C, 363.9°F, 457.6 K |
| Block | p | Density (g cm−3) | 4.933 |
| Atomic number | 53 | Relative atomic mass | 126.904 |
| State at 20°C | Solid | Key isotopes | 127I |
| Electron configuration | [Kr] 4d105s25p5 | CAS number | 7553-56-2 |
| ChemSpider ID | 4514549 | ChemSpider is a free chemical structure database | |
In the early 1800s, Bernard Courtois of Paris manufactured saltpetre (potassium nitrate, KNO3) and used seaweed ash as his source of potassium. One day in 1811, he added sulfuric acid and saw purple fumes which condensed to form crystals with a metallic lustre. Courtois guessed this was a new element. He gave some to Charles-Bernard Desormes and to Nicolas Clément who carried out a systematic investigation and confirmed that it was. In November 1813, they exhibited iodine at the Imperial Institute in Paris. That it really was new was proved by Joseph Gay-Lussac and confirmed by the Humphry Davy who was visiting Paris. Davy sent a report to the Royal Institution in London where it was mistakenly assumed he was the discoverer, a belief that persisted for more than 50 years.