Rubidium, Physical and Chemical Properties

Rubidium is a very reactive soft metal with a silvery luster and has the typical chemical properties of an alkali metal. It is more abundant in the Earth’s crust than lithium and cesium. Due to the similarity in their ionic radii, rubidium is always found in potash salt deposits, e.g., carnallite, sylvite, and langbeinite, which contain 10–300 g/t rubidium oxide. Rubidium is also widely distributed in very small concentrations in spring water, rivers, lakes, and seas. Its compounds are used in psychiatry and medicine, in magneto-optic modulators, solid-state lasers, phosphors (rubidium aluminate), Rb – C molecular sieves for hydrogen absorption, paper pigments, glass hardening by ion exchange, and components of electrolytes for fuel cells (Lenk and Prinz 1997).

Physical Properties

Atomic number	37
Atomic weight	85.468
Relative abundance in Earth’s crust, %	3.1 × 10−2
Density at 18°C, g/cm3	1.522
Density at m.p., g/cm3	1.472
Melting point, °C	39
Boiling point, °C	696
Ionization...