Radium
alkaline earth metal · period 7 · group 2 (alkaline earth metals) · s-block
Radium is a chemical element with the 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.
What the numbers say
At standard temperature and pressure Radium is a solid, sitting in period 7, group 2 of the s-block.
Its melting point of 1233 K (960 °C) is the 51st highest of the 110 elements with a measured value — mid-range among the elements.
At 5 g/cm³ it is the 63rd densest of 96 elements with a quoted density.
Pauling electronegativity is 0.9. Paired with oxygen (3.44) that is a difference of 2.54, which puts the bond predominantly ionic — expect a stable oxide ceramic.
In the solid state it takes a body-centered cubic structure — BCC packing is stronger but shows a ductile-to-brittle transition as temperature drops.
First identified in 1898.
Crystal structure
Solid Radium adopts a Body-centered Cubic arrangement, in the Cubic (isometric) system — axes a = b = c, angles α = β = γ = 90°. Symmetry controls the anisotropy of stiffness and thermal expansion, and the available slip systems set how far the metal deforms before it fractures.
Check it against computed structures
The structure search queries the Materials Project, OQMD and the Open Materials Database for computed crystal structures containing Ra — with DFT formation energy, hull stability and band gap where the provider publishes them.
K 2 · L 8 · M 18 · N 32 · O 18 · P 8 · Q 2
Properties
| Atomic number | 88 |
|---|---|
| Atomic mass | 226 u |
| Series | alkaline earth metal |
| Group | 2 |
| Period | 7 |
| Block | s-block |
| Phase at STP | Solid |
| Density | 5 g/cm³ |
| Melting point | 1233 K (960 °C) |
| Boiling point | 2010 K (1737 °C) |
| Electronegativity (Pauling) | 0.9 |
| Electron configuration | [Rn] 7s² |
| Crystal structure | Body-centered Cubic |
| Oxidation states | 2 |
| Discovered | 1898 |
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See Ra in context with all 118 elements.
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