All practice pages/Interatomic theory/Elements
Element 37, an alkali metal
A metal that melts on a hot day, catches fire in air, and keeps time in satellites and cell towers.
Period 5, group 1. The other alkali metals are tinted, and every cell opens its own article.
One valence electron, which rubidium gives up easily to form the Rb⁺ ion. Like the other alkali metals, it reacts with water.
More abundant in the crust than copper or zinc, but scattered through minerals such as lepidolite and pollucite with no ores of its own. It is recovered as a byproduct of lithium and cesium production.
Robert Bunsen and Gustav Kirchhoff found it in 1861 with their new spectroscope, in the mineral lepidolite, a year after they found cesium the same way. They named it from the Latin rubidus, deep red, for the color of its brightest spectral lines.
Atomic clocks, including many in GPS satellites and cell towers, and research on ultracold atoms: the first Bose-Einstein condensate, made in 1995, was a cloud of rubidium atoms. It also goes into photocells and specialty glass, and rubidium-strontium dating measures the age of rocks.
Catches fire on its own in air and reacts explosively with water, so it is sealed in glass under argon or oil.