Characteristics: Liquid at slightly above room temperature; soft solid below melting point. Highly reactive. Decomposes in water, with evolution of hydrogen, which ignites instantly. Also reacts violently with oxygen, the halogens, sulfur, and phosphorus, with spontaneous ignition and/or explosion. Mohs hardness 0.2. Cesium has highest position in the electromotive series; it also has the lowest melting point of any alkali metal, and the lowest ionization potential of any element. Soluble in acids and alcohol. Low toxicity.
Derivation: By thermochemical reduction of CsCl with calcium, or by electrolysis of fused cyanide. Its chief ore is pollucite, found in Maine, S. Dakota, Manitoba, Elba, S. Africa.
Hazard: Dangerous fire and explosion risk. Ignites spontaneously in moist air; may explode in contact with sulfur or phosphorus. Reacts violently with oxidizing materials. Causes burns on contact with skin.