Strontium (Sr)
[Kr] 5s². 0 unpaired electrons, period 5, group 2, 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.
SrStrontium, Z = 38, 87.62 u
[Kr] 5s2
In full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 5s²
- Blocks block
- Period5
- Group2
- Valence2
- Unpaired0
- MagneticDia
Last electron 5s
- n5shell
- l0s subshell
- m0orbital
- s−½spin down
Step by step
- Strontium has 38 electrons.
- Fill in (n + l) order: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s².
- Write the subshells in order of n: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 5s².
- Replace the krypton core with [Kr]: [Kr] 5s².
Strontium (Sr): the numbers
| Atomic number | 38 |
|---|---|
| Atomic mass | 87.62 u |
| Period | 5 |
| Group | 2 |
| Block | s block |
| Valence electrons | 2 |
| Unpaired electrons | 0 |
| Magnetic | diamagnetic |
| Last electron | 5s: n = 5, l = 0, m = 0, s = −1/2 |
Strontium (Sr): quick answers
What is the electronic configuration of strontium?
Strontium has 38 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 5s², or [Kr] 5s² in short.
How many unpaired electrons does strontium have?
Strontium has 0 unpaired electrons, so it is diamagnetic. 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 strontium?
The last electron goes into 5s: n = 5, l = 0, m = 0, s = −1/2. Orbitals fill from m = −l up, spin +½ first.