Rubidium - Rb
Rubidium (Rb) is a chemical element with atomic number 37. This page summarises its properties, uses and environmental context, with notes for water and process-treatment engineers.
Properties · Uses and occurrence · Health · Environment · Water and treatment
Chemical properties of rubidium
| Symbol / atomic number | Rb / 37 |
|---|---|
| Group / period / block | 1 / 5 / s |
| Standard atomic weight | 85.4678(3) |
| Electron configuration | [Kr] 5s1 |
| Common oxidation state(s) | +1 |
| Density (20 °C) | 1.53 g cm−3 |
| Melting point | 39.30 °C |
| Boiling point | 688 °C |
| Electronegativity (Pauling) | 0.82 |
| Non-bonded atomic radius | 0.303 nm |
| First ionisation energy | 403.032 kJ mol−1 |
| Representative isotopes | 85Rb, 87Rb |
| CAS registry number | 7440-17-7 |
Standard atomic weight follows CIAAW. Parentheses indicate uncertainty in the final quoted digits. Other physical and atomic data follow the Royal Society of Chemistry. Non-bonded atomic radii are method-dependent.
Rubidium: properties, uses and occurrence
Rubidium occurs in minerals such as lepidolite and pollucite, and is recovered as a by-product of lithium extraction. Its uses are limited, with applications in research, photocells, specialty glass and fireworks. The naturally occurring isotopes are 85Rb and radioactive 87Rb.
Health and safety
Rubidium has no established essential biological role. The chemical form and dose determine exposure; the violent water reaction applies to the metal itself and should not be confused with the behavior of dilute rubidium salts.
Rubidium in the environment
Weathering of rubidium-bearing minerals can release Rb+ to water and soil. Rubidium is chemically similar to potassium, but environmental occurrence and risk depend on concentration, source and exposure pathway.
Rubidium in water and treatment
For water analysis, report rubidium as a dissolved concentration and distinguish it from elemental rubidium metal. Conventional softeners are designed mainly for hardness ions, not selective Rb+ removal. If rubidium reduction is required, evaluate resin selectivity and competition from sodium and potassium in the actual water with treatability testing; account for the resulting regeneration stream. Do not infer removal from the reaction of rubidium metal with water.
Rubidium page last reviewed: by Lenntech.
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