Rubidium (Ru)
Rubidium (Ru)
Discovered in 1861, rubidium was first found by spectroscopy in the mineral lepidolite. The element is more abundant than originally believed; it also occurs in pollucite, leucite, zinnwaldite, and other minerals.
Rubidium is a soft and silvery metallic element that can be liquid at room temperature. It spontaneously ignites in air, reacts violently to water, and must be kept under oil or in inert atmospheres. It can form amalgams with mercury and alloys with gold, cesium, sodium, and potassium, and produces a yellowish violet flame. Twenty-four rubidium isotopes are known, and the naturally occurring form is radioactive and includes two isotopes. Rubidium also forms four oxides.
It is easily ionized, and consideration has been given to the element for use in an ion engine for space vehicles. It is used in vacuum tubes, photocells, and special glasses.