Rb
Rubidium
Element 37 · Alkali metal
Rubidium (Rb)
Rubidium is a soft, silvery alkali metal that melts just above body temperature and ignites in air.
- Alkali metal
- Period 5
- Group 1
- s-block
- solid at room temperature
Key properties
- Atomic mass
- 85.468
- u
- Electron configuration
- [Kr] 5s1
- Melting point
- 39.3 °C
- 312.46 K
- Boiling point
- 687.9 °C
- 961 K
- Density
- 1.53 g/cm³
- Electronegativity
- 0.82
- Pauling
- Atomic radius
- 303 pm
- van der Waals
- 1st ionisation energy
- 4.177 eV
Compare with every element:Electronegativity chartAtomic radius chartIonisation energy chartDensity chart of the elementsMelting point chartElectron configuration chart
Did you know?
Notable facts about rubidium
- 01
Rubidium was found with the newly invented spectroscope by its bright red spectral lines.
- 02
Rubidium atomic clocks keep time in GPS satellites and cell towers.
- 03
The first Bose–Einstein condensate, a new state of matter, was made from rubidium atoms in 1995.
Applications
What is rubidium used for?
- Atomic clocks
- Research in quantum physics
- Specialty glass
- Rock dating (rubidium–strontium)
History
Discovery & name origin
Discovered by
Year
Where
Germany
Name origin
Latin rubidus, “deep red”, for the red lines in its spectrum.
Atomic structure
Atomic properties
Atomic structure
Atomic properties
- Atomic number
- 37
- Atomic mass
- 85.468 u
- Group
- 1
- Period
- 5
- Block
- s-block
- Electron configuration
- [Kr] 5s1
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1
- Electrons per shell
- 2, 8, 18, 8, 1
- Electronegativity (Pauling)
- 0.82
- Electron affinity
- 0.468 eV
- Atomic radius (van der Waals)
- 303 pm
- Stable isotopes
- 1
Oxidation states
Highlighted: common oxidation states (+1).
Successive ionisation energies
Energy to remove each electron in turn (kJ/mol). Big jumps show where a new, inner shell begins.
- 1st403
- 2nd2,633
- 3rd3,860
- 4th5,080
- 5th6,850
- 6th8,140
- 7th9,570
- 8th13,120
Physical
Physical properties & colour
Physical
Physical properties & colour
- State at 20 °C
- Solid
- Melting point
- 312.46 K · 39.3 °C · 102.8 °F
- Boiling point
- 961 K · 687.9 °C · 1,270.1 °F
- Density
- 1.53 g/cm³
- Molar heat capacity
- 31.06 J/(mol·K)
- Appearance
- Grey white
- CPK model colour
- Copied
The CPK colour is the convention used for this element’s atoms in molecular models.
FAQ
Rubidium questions
What is Rb on the periodic table?
Rb is the symbol for rubidium, element 37 on the periodic table. It sits in group 1, period 5, in the alkali metal category, and has an atomic mass of 85.468.
What is the atomic number of rubidium?
Rubidium has atomic number 37, so every rubidium atom has 37 protons in its nucleus. Its symbol is Rb and its atomic mass is 85.468.
Who discovered rubidium?
Rubidium was discovered by Robert Bunsen and Gustav Kirchhoff in 1861 (Germany). The name comes from Latin rubidus, “deep red”, for the red lines in its spectrum.
What is rubidium used for?
Rubidium is used for: atomic clocks; research in quantum physics; specialty glass; rock dating (rubidium–strontium).
Is rubidium a metal?
Yes. Rubidium is a alkali metal, one of the metallic elements.
What is the electron configuration of rubidium?
The electron configuration of rubidium is [Kr] 5s1. Its 37 electrons are arranged in shells as 2, 8, 18, 8, 1.