Chlorine (Cl)

Chlorine is a yellow-green gas at room temperature and an extremely powerful oxidizing agent.

Core Principles & Analysis

• Carl Wilhelm Scheele prepared chlorine in 1774, but Humphry Davy showed in 1810 that the yellow-green gas was an element and named it.
• It is a dense, toxic, powerfully oxidizing gas, infamously used as a chemical weapon at Ypres in 1915.
• Chlorination of drinking water is one of public health's greatest advances, and chlorine is also essential to PVC plastic and household bleach.

Specifications & Metrics

• NUM: 17
• SYMBOL: Cl
• CATEGORY: Reactive Nonmetal
• ATOMIC MASS: 35.45 u
• ELECTRONEGATIVITY: 3.16 Pauling
• ATOMIC RADIUS: 175 pm
• IONIZATION ENERGY: 12.968 eV
• ELECTRON AFFINITY: 3.617 eV
• MELTING POINT: 171.65 K
• BOILING POINT: 239.11 K
• DENSITY: 0.003214 g/cm³
• ELECTRON CONFIGURATION: [Ne]3s2 3p5
• OXIDATION STATES: +7, +5, +1, -1
• STANDARD STATE: Gas
• GROUP BLOCK: Halogen
• YEAR DISCOVERED: 1774