Radium
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).
A stylized shell model. Electrons are quantum objects, not particles following these literal paths. Sizes and motion are illustrative.
86 is the [Rn] core total across six shells.
At a glance
- Atomic number
- 88
- Atomic mass
- 226 u
- Phase
- Solid
- Density
- 5.5 g/cm³
- Melting point
- 1,233 K
- Boiling point
- 2,010 K
- First ionization energy
- 509.3 kJ/mol
- Electronegativity
- 0.9
- Electron affinity
- 9.6485 kJ/mol
- Molar heat capacity
- Unavailable
- Period
- 7
- Appearance
- silvery white metallic
Conditions and isotopes affect measured properties. Some properties of short-lived elements are predicted. Electronegativity uses the Pauling scale.
Keep exploring
Explore the stories, imagery, and reference data in more depth. Properties with no value in the reference are marked unavailable.