Rubidium

Not to be confused with ruthenium.

Rubidium, 37Rb
Rubidium
Pronunciation/ruːˈbɪdiəm/ ​(roo-BID-ee-əm)
Appearancegrey white
Standard atomic weight Ar°(Rb)
Rubidium in the periodic table
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 Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver 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 Gold Mercury (element) Thallium Lead 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 Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
K
↑
Rb
↓
Cs
krypton ← rubidium → strontium
Atomic number (Z)37
Groupgroup 1: hydrogen and alkali metals
Periodperiod 5
Block  s-block
Electron configuration[Kr] 5s1
Electrons per shell2, 8, 18, 8, 1
Physical properties
Phase at STPsolid
Melting point312.45 K ​(39.30 °C, ​102.74 °F)
Boiling point961 K ​(688 °C, ​1270 °F)
Density (at 20° C)1.534 g/cm3[3]
when liquid (at m.p.)1.46 g/cm3
Triple point312.41 K, ​? kPa[4]
Critical point2093 K, 16 MPa (extrapolated)[4]
Heat of fusion2.19 kJ/mol
Heat of vaporization69 kJ/mol
Molar heat capacity31.060 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 434 486 552 641 769 958
Atomic properties
Oxidation statescommon: +1
−1?
ElectronegativityPauling scale: 0.82
Ionization energies
  • 1st: 403 kJ/mol
  • 2nd: 2632.1 kJ/mol
  • 3rd: 3859.4 kJ/mol
Atomic radiusempirical: 248 pm
Covalent radius220±9 pm
Van der Waals radius303 pm
Color lines in a spectral range
Spectral lines of rubidium
Other properties
Natural occurrenceprimordial
Crystal structure ​body-centered cubic (bcc) (cI2)
Lattice constant
Body-centered cubic crystal structure for rubidium
a = 569.9 pm (at 20 °C)[3]
Thermal expansion85.6×10−6/K (at 20 °C)[3]
Thermal conductivity58.2 W/(m⋅K)
Electrical resistivity128 nΩ⋅m (at 20 °C)
Magnetic orderingparamagnetic[5]
Molar magnetic susceptibility+17.0×10−6 cm3/mol (303 K)[6]
Young's modulus2.4 GPa
Bulk modulus2.5 GPa
Speed of sound thin rod1300 m/s (at 20 °C)
Mohs hardness0.3
Brinell hardness0.216 MPa
CAS Number7440-17-7
History
DiscoveryRobert Bunsen and Gustav Kirchhoff (1861)
First isolationGeorge de Hevesy
Isotopes of rubidium
Main isotopes[7] Decay
abun­dance half-life (t1/2) mode pro­duct
82Rb synth 1.2575 m β+ 82Kr
83Rb synth 86.2 d ε 83Kr
γ –
84Rb synth 32.9 d ε 84Kr
β+ 84Kr
γ –
β− 84Sr
85Rb 72.2% stable
86Rb synth 18.7 d β− 86Sr
γ –
87Rb 27.8% 4.923×1010 y β− 87Sr
 Category: Rubidium
| references

Rubidium is a chemical element; it has symbol Rb and atomic number 37. It is a very soft, whitish-grey solid in the alkali metal group, similar to potassium and caesium.[8] Rubidium is the first alkali metal in the group to have a density higher than water. On Earth, natural rubidium comprises two isotopes: 72% is a stable isotope 85Rb, and 28% is slightly radioactive 87Rb, with a half-life of 48.8 billion years – more than three times as long as the estimated age of the universe.

German chemists Robert Bunsen and Gustav Kirchhoff discovered rubidium in 1861 by the newly developed technique, flame spectroscopy. The name comes from the Latin word rubidus, meaning deep red, the color of its emission spectrum. Rubidium's compounds have various chemical and electronic applications. Rubidium metal is easily vaporized and has a convenient spectral absorption range, making it a frequent target for laser manipulation of atoms.[9] Rubidium is not a known nutrient for any living organisms. However, rubidium ions have similar properties and the same charge as potassium ions, and are actively taken up and treated by animal cells in similar ways.

  1. ^ "Standard Atomic Weights: Rubidium". CIAAW. 1969.
  2. ^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
  3. ^ a b c Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.
  4. ^ a b Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.122. ISBN 1-4398-5511-0.
  5. ^ Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
  6. ^ Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
  7. ^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  8. ^ Lenk, Winfried; Prinz, Horst; Steinmetz, Anja (2010). "Rubidium and Rubidium Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a23_473.pub2. ISBN 978-3527306732.
  9. ^ "Rubidium (Rb)". American Elements (americanelements.com). Retrieved 2024-03-27.