Symbol	Ra
Atomnummer	88
Gruppe	2 (Jordalkalimetaller)
Periode	7
Blok	s
Klassifikation	Jordalkalimetal

Udseende	Silvery white metallic
Farve	Sølv

Antal protoner	88 p+
Antal neutroner	138 n0
Antal elektroner	88 e-

Fra Wikipedia, den gratis encyklopædiRadium (af latin radius, "stråle") er det 88. grundstof i det periodiske system, og har det kemiske symbol Ra: Under normale temperatur- og trykforhold optræder dette stærkt radioaktive jordalkalimetal som et hvidt metal. Radium har kemiske egenskaber der minder om barium: Det angribes hurtigt af atmosfærisk luft, hvorved det bliver sort – muligvis på grund af et nitrid der dannes sammen med luftens indhold af kvælstof. Radium reagerer voldsomt med vand og sågar olie, under dannelse af radiumhydroxid og gasformig brint. Radium udsender en intens radioaktiv stråling af både alfa-, beta- og gammastråling, og denne stråling gør at prøver af stoffet "af sig selv" opretholder en temperatur lidt over omgivelsernes. Strålingen er desuden årsag til at stoffet udsender et svagt, blåligt lys.

Fase ved STP	Fast
Massefylde	5.5 g/cm3
Atommasse	226 u

Smeltepunkt	1233 K 959.85 °C 1759.73 °F
Kogepunkt	2010 K 1736.85 °C 3158.33 °F
Fordampningsvarme	136.82 kJ/mol

Elektronegativitet (Pauling Scale)	0.9
Elektronaffinitet	9.6485 kJ/mol
Oxidationstrin	+2 (expected to have a strongly basic oxide)
Ioniseringsenergier	509.3 kJ/mol 979 kJ/mol

Elektronkonfiguration Kortfattet konfiguration	[Rn] 7s2
Elektronkonfiguration Fuld konfiguration	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 7s2
Elektronkonfigurationsdiagram	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 7s2
Elektroner pr. Skal	2, 8, 18, 32, 18, 8, 2
Valenselektroner	2
Valency-elektroner	2
Bohrs atommodel	Figur: Skaldiagram af Radium (Ra) atom.
Orbital diagram 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 6s 6p 7s

Opdaget	Pierre Curie, Marie Curie (1898)
Første isolation	Marie Curie (1910)
Opdagelse af 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