Rubidium (Rb) – element 37
Rubidium is a chemical element with the symbol Rb and atomic number 37. It is a alkali metal in group 1 (alkali metals), period 5 of the periodic table (s-block), and is a solid at room temperature.
Rubidium (Rb) has atomic number 37, atomic mass 85.468 u and electron configuration [Kr] 5s1.
Rubidium facts
| Symbol | Rb |
|---|---|
| Atomic number | 37 |
| Atomic mass | 85.468 u (g/mol) |
| Category | alkali metal |
| Group | group 1 (alkali metals) |
| Period | 5 |
| Block | s-block |
| Phase at 20 °C | Solid |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 |
| Noble-gas notation | [Kr] 5s1 |
| Electrons per shell | 2, 8, 18, 8, 1 |
| Valence electrons | 1 |
Bohr model and shells
Rubidium has 37 electrons in 5 shells: 2, 8, 18, 8, 1. Full configuration and noble-gas notation are in the table; work out any element or ion with the electron configuration calculator.
Physical and atomic properties
| Melting point | 312.45 K (39.3 °C) |
|---|---|
| Boiling point | 961 K (687.9 °C) |
| Density | 1.532 g/cm³ |
| Electronegativity (Pauling) | 0.82 |
| Electron affinity | 46.884 kJ/mol |
| Ionization energies | 403, 2633, 3860 kJ/mol (1st, 2nd, 3rd) |
| Molar heat capacity | 31.06 J/(mol·K) |
| Discovered by | Robert Bunsen |
Use the atomic mass in the molar mass calculator for any formula containing Rb.
Position in the periodic table
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Frequently asked questions
What is the atomic mass of rubidium?
The atomic mass of rubidium is 85.468 u, so one mole of rubidium atoms weighs 85.468 g.
What is the electron configuration of rubidium?
Rubidium has 37 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s¹, or [Kr] 5s¹ in noble-gas notation. Electrons per shell: 2, 8, 18, 8, 1.
How many valence electrons does rubidium have?
Rubidium has 1 valence electron (group 1).
Is rubidium a metal?
Yes. Rubidium is a alkali metal.
Where is rubidium on the periodic table?
Rubidium is in group 1 (alkali metals), period 5, in the s-block.
Data: Periodic-Table-JSON (CC BY-SA 3.0); standard atomic weights from IUPAC (abridged). Values in brackets are the mass number of the longest-lived isotope.