Iodine

Element 53 on the periodic table, symbol I, group 17, period 5.

Iodine is a chemical element with symbol I and atomic number 53. The name is from Greek ἰοειδής ioeidēs, meaning violet or purple, due to the color of iodine vapor. Iodine and its compounds are primarily used in nutrition, and industrially in the production of acetic acid and certain polymers.

Appearance: lustrous metallic gray, violet as a gas

Properties

Atomic Number: 53
Atomic Mass: 126.9045 u
Group: 17
Period: 5
Block: p-block
Category: Diatomic Non-Metal
State at 25 °C: Solid
Melting Point: 386.9 K · 113.7 °C
Boiling Point: 457.4 K · 184.3 °C
Density: 4.933 g/cm³
Atomic Radius: 140 pm
Electronegativity: 2.66
Oxidation States: -1, +1, +5, +7
Abundance in Crust: 0.45 mg/kg
Discovered: 1811
Discovered By: Bernard Courtois

Electron Configuration

[Kr] 4d10 5s2 5p5

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p5

Ionisation Energies (kJ/mol)

1. 1,008.4
2. 1,845.9
3. 3,180

Elements near Iodine

Elements in the same group share the number of outer electrons and behave in similar ways. Elements in the same period share a shell, so they change steadily from left to right.