Iodine (I)

Iodine is a lustrous, purple-black nonmetallic solid that sublimes into a violet gas.

Core Principles & Analysis

• Bernard Courtois discovered iodine in 1811 when treating seaweed ash with sulfuric acid released violet vapors.
• The lustrous solid sublimes readily into a violet gas, and its name comes from the Greek word for violet.
• Iodine is essential for thyroid hormone synthesis, motivating iodized salt, and it is used in povidone-iodine antiseptics and X-ray contrast agents.

Specifications & Metrics

• NUM: 53
• SYMBOL: I
• CATEGORY: Reactive Nonmetal
• ATOMIC MASS: 126.9045 u
• ELECTRONEGATIVITY: 2.66 Pauling
• ATOMIC RADIUS: 198 pm
• IONIZATION ENERGY: 10.451 eV
• ELECTRON AFFINITY: 3.059 eV
• MELTING POINT: 386.85 K
• BOILING POINT: 457.55 K
• DENSITY: 4.93 g/cm³
• ELECTRON CONFIGURATION: [Kr]5s2 4d10 5p5
• OXIDATION STATES: +7, +5, +1, -1
• STANDARD STATE: Solid
• GROUP BLOCK: Halogen
• YEAR DISCOVERED: 1811