Symbol	Ra
Atomic number	88
Group	2 (Alkaline earth metal)
Period	7
Block	s
Classification	Alkaline Earth Metal

Appearance	Silvery white metallic
Color	Silver

Number of protons	88 p+
Number of neutrons	138 n0
Number of electrons	88 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).

Phase at STP	Solid
Density	5.5 g/cm3
Atomic weight	226 u

Melting point	1233 K 959.85 °C 1759.73 °F
Boiling point	2010 K 1736.85 °C 3158.33 °F
Heat of vaporization	136.82 kJ/mol

Electronegativity (Pauling Scale)	0.9
Electron affinity	9.6485 kJ/mol
Oxidation states	+2 (expected to have a strongly basic oxide)
Ionization energies	509.3 kJ/mol 979 kJ/mol

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	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 7s2
Electrons per shell	2, 8, 18, 32, 18, 8, 2
Valence electrons	2
Valency electrons	2
Bohr model	Figure: Shell diagram of Radium (Ra) atom.
Orbital Diagram 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 6s 6p 7s

Discovery	Pierre Curie, Marie Curie (1898)
First isolation	Marie 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.

CAS Number	7440-14-4
ChemSpider ID	4886483
EC number	231-122-4
PubChem CID Number	6328144