Radium (Ra)
Radium is element 88, a alkaline earth metal in period 7, group 2 of the periodic table. At room temperature it is a solid.
Electron configuration [Rn] 7s2
Electrons per shell 2, 8, 18, 32, 18, 8, 2
Radium data
| Atomic number | 88 |
|---|---|
| Symbol | Ra |
| Atomic mass | [226] (mass number of the longest-lived isotope) |
| Category | Alkaline earth metal |
| Group | 2 |
| Period | 7 |
| Block | s |
| State at 25 °C | solid |
| Melting point | 973 K (699.9 °C) |
| Boiling point | 2010 K (1736.9 °C) |
| Density | 5 g/cm³ |
| Electronegativity (Pauling) | 0.9 |
| Atomic radius | — |
| 1st ionization energy | 509 kJ/mol |
| Electron affinity | — |
| Oxidation states | +2 |
| Common ion charge | 2+ |
| Discovered | 1898 |
Orbital diagram
Each box is one orbital holding up to two electrons of opposite spin. Following Hund’s rule, electrons spread out singly across a subshell before pairing.
Work through radium’s configuration and its ions →
Where radium sits
Radium belongs to the alkaline earth metals. Its Pauling electronegativity of 0.9 is among the lowest on the table, so it gives up electrons readily; see the electronegativity chart and periodic trends for context. To use its mass in a calculation, try the molar mass calculator.
Radium FAQ
What is the electron configuration of radium?
Radium (Z = 88) has the configuration 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f14 5d10 6s2 6p6 7s2. In noble-gas shorthand that is [Rn] 7s2.
How many valence electrons does radium have?
2 (outer shell (n = 7)).
What is the atomic mass of radium?
Radium has no stable isotopes. Its most stable known isotope has mass number 226, so tables list [226].
Is radium a metal?
Yes. Radium is a alkaline earth metal.
What is the charge of a radium ion?
Radium most commonly forms Ra2+.