Periodic TableRadium (Ra)
Radium is an alkaline earth metal with atomic number 88, in period 7 and group 2 of the periodic table. Its atomic mass is 226 u and its electron configuration is [Rn] 7s². Solid at 25 °C.
Key facts
| Atomic number | 88 |
|---|---|
| Atomic mass | 226 u |
| Category | Alkaline Earth Metal |
| Period | 7 |
| Group | 2 |
| Block | s |
| Electron configuration | [Rn] 7s² |
| Electrons per shell | 2, 8, 18, 32, 18, 8, 2 |
| Electronegativity (Pauling) | 0.9 |
| Oxidation states | +2common in bold |
| State at 25 °C | Solid |
| Melting point | 973 K699.85 °C |
| Boiling point | 1413 K1139.85 °C |
| Density | 5 g/cm³ |
Atomic properties
| First ionization energy | 5.279 eV |
|---|---|
| Electron affinity | --- |
| Atomic radius | 215 pm |
| Covalent radius | 221 pm |
| Van der Waals radius | 283 pm |
| Common ions | Ra_{2+} |
| Protons, neutrons, electrons | 88, 138, 88 |
Physical and thermal properties
| Molar volume | 41.09 cm³/mol |
|---|---|
| Heat of fusion | 8 kJ/mol |
| Heat of vaporization | 125 kJ/mol |
| Specific heat | 92 J/(kg·K) |
| Thermal conductivity | 19 W/(m·K) |
| Thermal expansion | --- |
| Mohs hardness | --- |
| Young’s modulus | --- |
| Crystal structure | Body-centered cubic |
| Magnetic type | --- |
Identification and history
| CAS number | 7440-14-4 |
|---|---|
| Latin name | Radium |
| Discovered by | Pierre and Marie Curie · 1898 |
| Named by | --- |
Natural isotopes
Radium has no stable isotopes: every isotope is radioactive.
Data checked against PubChem (NIH), IUPAC, the NIST Atomic Spectra Database and the IAEA (NUBASE and AME), the same data you see in the app.
A dash (---) means there is no reliable published measurement. The app never makes one up.
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