88
Ra
Radium
226
Radium (Ra)
Alkaline Earth MetalGroup 2Period 7s-block-blockRadioactive
Radium 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).
Latin name: Radium
Atomic Number
88
Atomic Mass
226 g/mol
Phase (STP)
Solid
Electron Config.
[Rn] 7s²
General
SymbolRa
Atomic Number88
Atomic Mass226 g/mol
CategoryAlkaline Earth Metal
Group2
Period7
Blocks-block
Electron Configuration[Rn] 7s²
Valence Electrons2
Coloursilvery-white metallic
Appearancesilvery white metallic
CAS NumberCAS7440-14-4
Physical Properties
Phase (STP)Solid
Density5.5 g/cm³
Melting Point699.85°C · 1291.73°F · 973.00 K
Boiling Point1736.85°C · 3158.33°F · 2010.00 K
Atomic Properties
Atomic Radius283 pm
Electronegativity0.9 Pauling
Ionization Energy509 kJ/mol
Oxidation States+2
Ion ChargeRa2+
Crystal Structure
Crystal Structureface-centered cubic
Nuclear & Hazards
RadioactiveYes
Half-life1600 years (Ra-226)
Abundance
In Universe0.00000000001%
In Earth's Crust0.00000000001%
Discovery & History
Discovery Year1898
Discovered ByMarie Curie, Pierre Curie, G. Bemont and P. Bémont
Country of DiscoveryFrance/Poland
Isotopes of Radium
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| Ra-223 | — | 11.435 days | α |
| Ra-224 | — | 3.6319 days | α |
| Ra-225 | — | 14.9 days | β⁻ |
| Ra-226 | — | 1600 years | α |
| Ra-228 | — | 5.75 years | β⁻ |