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Radium,  88Ra
General properties
Name, symbol Radium, Ra
Appearance Silvery white metallic
Radium in the periodic table


Francium ← Radium → Actinium
Atomic number 88
Standard atomic weight (Ar) 226
Group, block , s-block
Period period 7
Electron configuration [Rn] 7s2
per shell
2, 8, 18, 32, 18, 8, 2
Physical properties
Silvery white metallic
Phase Solid
Melting point 973 K ​(700 °C, ​1292 °F)
Boiling point 2010 K ​(1737 °C, ​3159 °F)
Density near r.t. 5.5 g/cm3
Heat of fusion 8.5 kJ/mol
Heat of 113 kJ/mol
Atomic properties
Oxidation states +2
Electronegativity Pauling scale: 0.9
energies 1st: 509.3 kJ/mol
2nd: 979.0 kJ/mol
Covalent radius 221±2 pm
Van der Waals radius 283 pm
Crystal structure ​Body-centered cubic (bcc)
Thermal conductivity 18.6 W/(m·K)
Electrical resistivity 1 Ω·m (at 20 °C)
CAS Registry Number 7440-14-4
Discovery Pierre and Marie Curie (1898)
First isolation Marie Curie (1910)
· references

Radium is a chemical element with symbol Ra and atomic number 88. All isotopes of radium are highly radioactive, with the most stable isotope being radium-226, which has a half-life of 1600 years and decays into radon gas (specifically the isotope radon-222). When radium decays, ionizing radiation is a product, which can excite fluorescent chemicals and cause radioluminescence.



Radium metal readily reacts with nitrogen on exposure to air, forming a black surface layer of radium nitride (Ra3N2).


Radium is a silvery white metal, that quickly tarnishes in air forming a black surface of radium nitride.


Radium was used in the past in fluorescent paint used for clock and watch indicators, now replaced by the more safe tritium.

Pure radium metal is extremely difficult to get hold of, as it doesn't have common uses and it's very expensive. Likewise, since it's a radioactive material, a permit may be required for it.

In nature, radium is found in uranium ores, most often in pitchblende. One ton of pitchblende typically yields about one seventh of a gram of radium.


Radium can be isolated from uranium minerals. Isolation from old radium paint is also possible, but you will need an enormous amount of it, and that amount of radium is unsafe to handle without proper protection.

One student from Austria was able to isolate 0.5 µg of radium in the form of radium carbonate from uranothorianite.[1]




Radium is highly radioactive and its immediate daughter, radon gas, is also radioactive. When ingested, 80% of the ingested radium leaves the body through the feces, while the other 20% goes into the bloodstream, mostly accumulating in the bones. Exposure to radium, internal or external, can cause cancer and other disorders, because radium and radon emit alpha and gamma rays upon their decay, which kill and/or mutate cells.


Radium must be kept in ampoules at all times to prevent radon gas from being released in closed chambers and to prevent oxidation.


Burying it in concrete or in a place with natural deposits of radioactive minerals is a possible choice.


  1. http://theodoregray.com/periodictable/Elements/088/index.s7.html#sample13

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