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 : 85 Rb, the anly stable ane, constitutes 72% o it. The remainin 28% is the slichtly radioactive 87 Rb wi a hauf-life o 49 billion year—mair nor three times langer than the estimatit age o the universe.
Rubidium, 37 Rubidium Pronunciation (roo-BID -ee-əm Appearance grey white Standard atomic weight A r, std (Rb) 7001854678000000000♠ 85.4678(3)[1] Rubidium in the periodic cairt 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[2] Creetical pynt 2093 K, 16 MPa (extrapolatit) [2] 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 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)[3] r.t. ) Thermal conductivity 58.2 W/(m·K) Electrical resistivity 128 nΩ·m (at 20 °C) Magnetic orderin paramagnetic[4] 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 83 Rbsyn 86.2 d ε 83 Krγ 84 Rbsyn 32.9 d ε 84 Krβ+ 84 Krγ β− 84 Sr85 Rb72.17% stable 86 Rbsyn 18.65 d β− 86 Srγ 87 Rb27.83% 4.9× 1010 β− 87 Sr
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