Radium (Ra)

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).

Radium in the periodic table

Atomic number88
Element categoryAlkaline Earth Metal

Physical properties

Phase at STPSolid
Density5.5 g/cm3
Atomic weight226 u
Melting point1233 K
959.85 °C
1759.73 °F
Boiling point2010 K
1736.85 °C
3158.33 °F

Atomära egenskaper

Electronegativity (Pauling Scale)0.9
Electron affinity9.6485 kJ/mol
Ionization energies
1509.3 kJ/mol
2 979 kJ/mol

Electron configuration

Electron configuration1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 7s2
Electrons per shell2, 8, 18, 32, 18, 8, 2


Discovered byPierre Curie
Marie Curie