Iodine (symbol I, atomic number 53) is a halogen essential to the thyroid gland and used as an antiseptic. It is classified as a halogen and sits in group 17, period 5 of the periodic table.
Overview
Iodine is the chemical element with atomic number 53 and the symbol I. With a standard atomic weight of 126.9, it is a halogen. In the periodic table it occupies group 17 and period 5, and under standard conditions it is normally a solid. Iodine is a halogen essential to the thyroid gland and used as an antiseptic.
Atomic structure
An atom of Iodine has 53 protons in its nucleus and, when neutral, 53 electrons arranged in the configuration [Kr] 4d10 5s2 5p5. Its standard atomic weight of 126.9 reflects the natural mix of its stable isotopes.
Discovery and place in the table
Iodine was discovered in 1811 by Bernard Courtois. It follows Tellurium (Te) and precedes Xenon (Xe) in order of atomic number.
| Atomic number | 53 |
|---|---|
| Symbol | I |
| Atomic mass | 126.9 |
| Category | Halogen |
| Group | 17 |
| Period | 5 |
| Electron configuration | [Kr] 4d10 5s2 5p5 |
| Phase at STP | Solid |
| Discovered | 1811 (Bernard Courtois) |