Rubidium (Rb)
[Kr] 5s¹. 1 unpaired electron, period 5, group 1, s block.
Element or ion
Type a symbol, a name or an atomic number, add a charge such as Fe3+ or Cl-, or tap an element in the table. Orbitals fill from m = −l up, spin +½ first.
RbRubidium, Z = 37, 85.468 u
[Kr] 5s1
In full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 5s¹
- Blocks block
- Period5
- Group1
- Valence1
- Unpaired1
- MagneticPara
Last electron 5s
- n5shell
- l0s subshell
- m0orbital
- s+½spin up
Step by step
- Rubidium has 37 electrons.
- Fill in (n + l) order: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s¹.
- Write the subshells in order of n: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 5s¹.
- Replace the krypton core with [Kr]: [Kr] 5s¹.
Rubidium (Rb): the numbers
| Atomic number | 37 |
|---|---|
| Atomic mass | 85.468 u |
| Period | 5 |
| Group | 1 |
| Block | s block |
| Valence electrons | 1 |
| Unpaired electrons | 1 |
| Magnetic | paramagnetic |
| Last electron | 5s: n = 5, l = 0, m = 0, s = +1/2 |
Rubidium (Rb): quick answers
What is the electronic configuration of rubidium?
Rubidium has 37 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 5s¹, or [Kr] 5s¹ in short.
How many unpaired electrons does rubidium have?
Rubidium has 1 unpaired electron, so it is paramagnetic. Put one electron in each box of a subshell before pairing (Hund’s rule) to see them.
What are the quantum numbers of the last electron of rubidium?
The last electron goes into 5s: n = 5, l = 0, m = 0, s = +1/2. Orbitals fill from m = −l up, spin +½ first.