Atomic Properties of Rb
- Atomic Number of Rb
- 37
- Atomic Mass of Rb
- 85.4680 u
- Electron Configuration
- [Kr] 5s1
- Electronegativity
- 0.82
- Block
- s-block
- Group
- 1
- Period
- 5
Rubidium was discovered before anyone isolated a useful sample. In 1861, Robert Bunsen and Gustav Kirchhoff examined a mineral with a spectroscope and found unfamiliar deep-red lines. They named the new element from rubidus, Latin for deep red. Light had revealed an element hidden among chemically similar alkali metals.
The pure metal is soft, silvery, and extraordinarily reactive. Rubidium can ignite in air and reacts violently with water, so it is sealed away from both. Its compounds are more manageable and appear in specialized research, photocells, catalysts, and vacuum equipment. Rubidium is widespread in minerals but rarely concentrated enough to mine as a principal product; it is often recovered during lithium processing.
Two isotopes dominate natural rubidium. Rubidium-85 is stable. Rubidium-87 is radioactive, but its half-life is about 49.7 billion years, more than three times the age of the universe. It slowly decays to strontium-87. Comparing rubidium and strontium isotope ratios lets geologists date ancient rocks and reconstruct when minerals formed.
A different atomic transition makes rubidium useful for compact atomic clocks. These clocks are generally less accurate than primary cesium standards, but their size, cost, and stability suit telecommunications, navigation equipment, and laboratory instruments. One element supplies a clock measured in microwave oscillations and another measured across geological eras.
Rubidium starts with a flash of red in a spectroscope, then stretches time in both directions. Its reactive metal lasts poorly in air; its atomic transitions count moments; its radioactive isotope records billions of years.