Rubidium Rb 37

Rubidium Rb 37 is a chemical element with symbol Rb and atomic number 37. Rubidium is a soft, silvery-white metallic element of the alkali metal group, with an atomic mass of 85.4678. Elemental rubidium is highly reactive, with properties similar to those of other alkali metals, including rapid oxidation in air. On Earth, natural rubidium comprises two isotopes: 72% is the stable isotope, ⁸⁵Rb; 28% is the slightly radioactive ⁸⁷Rb, with a half-life of 49 billion years—more than three times longer than the estimated age of the universe.

German chemists Robert Bunsen and Gustav Kirchhoff discovered rubidium in 1861 by the newly developed technique, flame spectroscopy.

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.

Rubidium is not a known nutrient for any living organisms. However, rubidium ions have the same charge as potassium ions, and are actively taken up and treated by animal cells in similar ways.

Rubidium is a very soft, ductile, silvery-white metal.It is the second most electropositive of the non-radioactive alkali metals and melts at a temperature of 39.3 °C (102.7 °F). Similar to other alkali metals, rubidium metal reacts violently with water. As with potassium (which is slightly less reactive) and caesium (which is slightly more reactive), this reaction is usually vigorous enough to ignite the hydrogen gas it produces. Rubidium has also been reported to ignite spontaneously in air.It forms amalgams with mercury and alloys with gold, iron, caesium, sodium, and potassium, but not lithium (even though rubidium and lithium are in the same group).

Rubidium has a very low ionization energy of only 406 kJ/mol.Rubidium and potassium show a very similar purple color in the flame test, and distinguishing the two elements requires something more sophisticated, such as spectroscopy.

General properties
Pronunciation	/rʊˈbɪdiəm/ ruu-BID-ee-əm
Appearance	grey white
Rubidium in the periodic table
K ↑ Rb ↓ Cs krypton ← rubidium → strontium ‍
Atomic number (Z)	37
Group, period	group 1 (alkali metals), period 5
Block	s-block
Element category	alkali metal
Standard atomic weight (Ar)	85.4678(3)[1]
Electron configuration	[Kr] 5s1
Electrons per shell	2, 8, 18, 8, 1
Physical properties
Phase	solid
Melting point	312.45 K ​(39.30 °C, ​102.74 °F)
Boiling point	961 K ​(688 °C, ​1270 °F)
Density near r.t.	1.532 g/cm3
when liquid, at m.p.	1.46 g/cm3
Triple point	312.41 K, ​? kPa[2]
Critical point	2093 K, 16 MPa (extrapolated)[2]
Heat of fusion	2.19 kJ/mol
Heat of vaporization	69 kJ/mol
Molar heat capacity	31.060 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