# Rubidium

Rubidium, 37Rb|  |
| Rubidium |
| Pronunciation | /ruːˈbɪdiəm/ ​(*roo-**BID**-ee-əm*) |
| Appearance | grey white |
| Standard atomic weight *A*r, std(Rb) | 7001854678000000000♠85.4678(3) |
| Rubidium in the periodic cairt |
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|  |  |  |
| --- | --- | --- |
| Hydrogen |  | Helium |
| Lithium | Beryllium |  | Boron | Carbon | Nitrogen | Oxygen | Fluorine | Neon |
| Sodium | Magnesium |  | Aluminium | Silicon | Phosphorus | Sulfur | Chlorine | Argon |
| Potassium | Calcium |  | Scandium | Titanium | Vanadium | Chromium | Manganese | Airn | Cobalt | Nickel | Capper | Zinc | Gallium | Germanium | Arsenic | Selenium | Bromine | Krypton |
| Rubidium | Strontium |  |  | Yttrium | Zirconium | Niobium | Molybdenum | Technetium | Ruthenium | Rhodium | Palladium | Siller (element) | Cadmium | Indium | Tin | Antimony | Tellurium | Iodine | Xenon |
| Caesium | Barium | Lanthanum | Cerium | Praseodymium | Neodymium | Promethium | Samarium | Europium | Gadolinium | Terbium | Dysprosium | Holmium | Erbium | Thulium | Ytterbium | Lutetium | Hafnium | Tantalum | Tungsten | Rhenium | Osmium | Iridium | Platinum | Gowd | Mercur (element) | Thallium | Leid (element) | Bismuth | Polonium | Astatine | Radon |
| Francium | Radium | Actinium | Thorium | Protactinium | Uranium | Neptunium | Plutonium | Americium | Curium | Berkelium | Californium | Einsteinium | Fermium | Mendelevium | Nobelium | Lawrencium | Rutherfordium | Dubnium | Seaborgium | Bohrium | Hassium | Meitnerium | Darmstadtium | Roentgenium | Copernicium | Ununtrium | Flerovium | Ununpentium | Livermorium | Ununseptium | Ununoctium |

 | K ↑ **Rb** ↓ Cs |
| krypton ← **rubidium** → strontium |

 |

 |
| Atomic nummer (*Z*) | 37 |
| Group | group 1 (alkali metals) |
| Period | period 5  |
| Block | s-block  |
| Element category |   Alkali metal |
| Electron confeeguration | [Kr] 5s1 |
| Electrons per shell | 2, 8, 18, 8, 1 |
| Pheesical properties |
| Phase at STP | solit |
| Meltin pynt | 312.45 K ​(39.30 °C, ​102.74 °F)  |
| Bylin pynt | 961 K ​(688 °C, ​1270 °F)  |
| Density (near r.t.) | 1.532 g/cm3 |
| when liquid (at m.p.) | 1.46 g/cm3  |
| Treeple pynt | 312.41 K, ​? kPa  |
| Creetical pynt | 2093 K, 16 MPa *(extrapolatit)* |
| Heat o fusion | 2.19 kJ/mol  |
| Heat o vapourisation | 69 kJ/mol  |
| Molar heat capacity | 31.060 J/(mol·K)  |
| **Vapour pressur**

| *P* (Pa) | 1 | 10 | 100 | 1 k | 10 k | 100 k |
| --- | --- | --- | --- | --- | --- | --- |
| at *T* (K) | 434 | 486 | 552 | 641 | 769 | 958 |

 |
| Atomic properties |
| Oxidation states | −1, **+1** strangly basic |
| Electronegativity | Pauling scale: 0.82  |
| Ionisation energies | * 1st: 403 kJ/mol
* 2nd: 2632.1 kJ/mol
* 3rd: 3859.4 kJ/mol
*
 |
| Atomic radius | empirical: 248 pm  |
| Covalent radius | 220±9 pm  |
| Van der Waals radius | 303 pm  |
| Colour lines in a spectral range**Spectral lines o rubidium** |
| Ither properties |
| Naitural occurrence | primordial |
| Creestal structur |  ​body-centred cubic (bcc) |
| Speed o soond  thin rod | 1300 m/s (at 20 °C)  |
| Thermal expansion | 90 µm/(m·K) (at r.t.) |
| Thermal conductivity | 58.2 W/(m·K)  |
| Electrical resistivity | 128 nΩ·m (at 20 °C)  |
| Magnetic orderin | paramagnetic  |
| Young's modulus | 2.4 GPa  |
| Bulk modulus | 2.5 GPa  |
| Mohs haurdness | 0.3  |
| Brinell haurdness | 0.216 MPa  |
| CAS Nummer | 7440-17-7  |
| History |
| Diskivery | Robert Bunsen an Gustav Kirchhoff (1861) |
| First isolation | George de Hevesy |
| Main isotopes o rubidium |
|

| Iso­tope | Abun­dance | Hauf-life (*t*1/2) | Decay mode | Pro­duct |
| --- | --- | --- | --- | --- |
| 83Rb | syn | 86.2 d | ε | 83Kr |
| γ | – |
| 84Rb | syn | 32.9 d | ε | 84Kr |
| β+ | 84Kr |
| γ | – |
| β− | 84Sr |
| 85Rb | 72.17% | stable |
| 86Rb | syn | 18.65 d | β− | 86Sr |
| γ | – |
| 87Rb | 27.83% | 4.9×1010 y | β− | 87Sr |

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**Rubidium** is a chemical element wi seembol **Rb** an atomic nummer 37. Rubidium is a saft, sillery-white metallic element o the alkali metal group, wi an atomic mass o 85.4678. Elemental rubidium is heichly reactive, wi properties seemilar tae those o ither alkali metals, sic as very rapid oxidation in air. Naitural rubidium is a mix o twa isotopes: 85Rb, the anly stable ane, constitutes 72% o it. The remainin 28% is the slichtly radioactive 87Rb wi a hauf-life o 49 billion year—mair nor three times langer than the estimatit age o the universe.