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Radium (Ra)

Radium is a chemical element of the periodic table with chemical symbol Ra and atomic number 88 with an atomic weight of 226 u and is classed as alkaline earth metal and is part of group 2 (alkaline earth metal). Radium is solid at room temperature.

Radium in the periodic table

Atomic number88
Group2 (Alkaline earth metal)
ClassificationAlkaline Earth Metal
AppearanceSilvery white metallic
Color Silver
Number of protons88 p+
Number of neutrons138 n0
Number of electrons88 e-
From Wikipedia, the free encyclopediaRadium is a chemical element with symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is almost colorless, but it readily combines with nitrogen (rather than oxygen) on exposure to air, forming a black surface layer of radium nitride (Ra3N2).

Physical properties

Phase at STPSolid
Density5.5 g/cm3
Atomic weight226 u

Thermal properties

Melting point1233 K
959.85 °C
1759.73 °F
Boiling point2010 K
1736.85 °C
3158.33 °F
Heat of vaporization136.82 kJ/mol

Atomic properties

Electronegativity (Pauling Scale)0.9
Electron affinity9.6485 kJ/mol
Oxidation states+2
(expected to have a strongly basic oxide)
Ionization energies
  1. 509.3 kJ/mol
  2. 979 kJ/mol

Electron configuration for radium

Electron configuration
Shorthand configuration
[Rn] 7s2
Electron configuration
Full configuration
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 7s2
Electron configuration chart
Electrons per shell2, 8, 18, 32, 18, 8, 2
Valence electrons 2
Valency electrons 2
Bohr model
RadiumElectron shell for Radium, created by Injosoft ABRa
Figure: Shell diagram of Radium (Ra) atom.
Orbital Diagram

The history of Radium

DiscoveryPierre Curie, Marie Curie (1898)
First isolationMarie Curie (1910)
Discovery of radium
Radium, in the form of radium chloride, was discovered by Marie Skłodowska-Curie and her husband Pierre Curie on 21 December 1898, in a uraninite (pitchblende) sample from Jáchymov. They extracted the radium compound from uraninite and published the discovery at the French Academy of Sciences five days later. Radium was isolated in its metallic state by Marie Curie and André-Louis Debierne through the electrolysis of radium chloride in 1911. The naming of radium dates to about 1899, from the French word radium, formed in Modern Latin from radius (ray): this was in recognition of radium's power of emitting energy in the form of rays. In September 1910, Marie Curie and André-Louis Debierne announced that they had isolated radium as a pure metal through the electrolysis of pure radium chloride (RaCl2) solution using a mercury cathode, producing radium–mercury amalgam. This amalgam was then heated in an atmosphere of hydrogen gas to remove the mercury, leaving pure radium metal.


List of unique identifiers for Radium in various chemical registry databases
CAS Number7440-14-4
ChemSpider ID4886483
EC number231-122-4
PubChem CID Number6328144