Radium (Ra)
Radium (Ra) is element 88 of the periodic table, an alkaline earth metal in period 7 and group 2. It has no stable isotope and no standard atomic weight; 226 is the mass number of its longest-lived isotope. At room temperature it is a solid; it melts at 699.85 °C and boils at 1139.85 °C.
| Atomic number | 88 |
|---|---|
| Symbol | Ra |
| Standard atomic weight | [226] (mass number of the longest-lived isotope) |
| Molar mass | [226] g/mol |
| Category | Alkaline earth metal |
| Group | 2 |
| Period | 7 |
| Block | s-block |
| Electron configuration | [Rn] 7s2 |
| Oxidation states | +2 |
| Electronegativity (Pauling) | 0.9 |
| Atomic radius (van der Waals) | 283 pm |
| First ionisation energy | 5.279 eV (509.3 kJ/mol) |
| Electron affinity | — |
| State at room temperature | Solid |
| Melting point | 973 K (699.85 °C) |
| Boiling point | 1413 K (1139.85 °C) |
| Density | 5 g/cm³ |
| Discovered | 1898 |
Group 2
Calculate with Radium
Atomic weight: IUPAC CIAAW — no standard atomic weight; mass number in brackets. Other properties: PubChem (U.S. National Library of Medicine, public domain). Values such as melting point and radius depend on how they were measured; check a data book for precise work.