You are here

Rubidium Element in Periodic Table | Atomic Number Atomic Mass


Rubidium Element:

Rubidium is an element in the first group of periodic table. Since all the elements in the first group of periodic table are alkali metals, rubidium is also an alkali metal.

Like all the alkali metals, rubidium has one electron in its outermost orbital and its combining capacity or valency is one. The atomic number  is 37. It has a tendency to attain stable electronic configuration of the inert gas (present in the 4th period) called krypton, by losing its electron to an atom with affinity to gain one electron for attaining stable electronic configuration. Like all the atoms of alkalis, it has a tendency to lose electron to form a stable compound, it is said to be electropositive.

Rubidium in its elemental form is highly reactive and when it comes in contact with air, it reacts with oxygen to form its oxide. It also reacts violently with water to liberate hydrogen exothermically and forms its own hydroxide, RbOH.

Though rubidium has two naturally occurring isotopes, the stable 85Rb and the radioactive 87Rb, additional twenty four isotopes have been artificially synthesized which are highly radioactive with half-life periods of less than three months. The most stable isotope 87Rb is used for dating/assessing the age of rocks for geological studies.


Rubidium is used in thermo electric generators by passing hot rubidium ions through magnetic field for generating electricity. Vaporized rubidium is used in laser cooling and Bose-Einstein condensation. The compounds of rubidium are used for recreational purposes as they generate attractive purple color when fireworks are burn.

It is used in making of high-precision atomic clocks. The isotopic 82Rb is used for locating and imaging brain tumors, helping in clinical diagnosis.


Rubidium Element Information:

Discovery year: 1861

Discovered by: Robert Bunsen and Gustav Kirchhoff

Atomic number: 37

Relative atomic mass: 85.468  

Electron configuration: [Kr] 5s1

Block: s-block 

Other elements in the same block:

Hydrogen, Helium, Lithium, Beryllium, Sodium, Magnesium, Potassium, Calcium, Strontium, Caesium, Barium, francium and Radium are other elements in the s-block.

Period: period 5

Other elements in the same period:

Strontium, Yttrium, Zirconium, Niobium, Molybdenum, Technetium, Ruthenium, Rhodium, Palladium, Silver, Cadmium, Indium, Tin, Antimony, Tellurium, Iodine and Xenon

Group: group 1 (alkali metals)

Other elements in the same group:

Hydrogen, Lithium, Sodium, Potassium, Caesium and   francium

Other elements in the same orbital:

Strontium is the element in the same orbital.

Allotropes: none

Key isotopes: 85Rb, 87Rb 

Melting point: 39.30°C, 102.74°F, 312.45 K 

Boiling point: 688°C, 1270°F, 961 K 

Element category:  alkali metal

Density (g cm−3): 1.53 

CAS number: 7440-17-7 

Color: grey white

You can know detailed information for each element,

Hydrogen, HeliumLithiumBerylliumBoronCarbonNitrogenOxygenFluorine,  Neon , SodiumMagnesiumAluminiumSiliconPhosphorusSulfurChlorineArgon, PotassiumCalciumScandiumTitaniumVanadiumChromiumManganeseIronCobaltNickelCopperZincGalliumGermaniumArsenicSeleniumBromine, Krypton,  Rubidium, StrontiumYttriumZirconiumNiobiumMolybdenumTechnetiumRutheniumRhodiumPalladiumSilverCadmiumIndiumTinAntimonyTelluriumIodine, Xenon,  Caesium, BariumLanthanum,  CeriumPraseodymiumNeodymiumPromethiumSamariumEuropiumGadoliniumTerbiumDysprosiumHolmiumErbiumThuliumYtterbiumLutetiumHafniumTantalumTungstenRheniumOsmiumIridiumPlatinumGoldMercuryThalliumLeadBismuthPoloniumAstatine, Radon,  Francium, RadiumActiniumThoriumProtactiniumUraniumNeptuniumPlutoniumAmericiumCuriumBerkeliumCaliforniumEinsteiniumFermiumMendeleviumNobeliumLawrenciumRutherfordiumDubniumSeaborgiumBohriumHassiumMeitneriumDarmstadtiumRoentgeniumCoperniciumNihoniumFleroviumMoscoviumLivermoriumTennessine, Oganesson.

Add new comment

This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.
3 + 0 =
Solve this simple math problem and enter the result. E.g. for 1+3, enter 4.