Strontium (Sr): electron configuration, atomic mass and facts
Strontium (Sr) is element 38 of the periodic table, an alkaline earth metal in period 5, group 2. Its electron configuration is [Kr] 5s2, with electrons arranged in shells 2, 8, 18, 8, 2, and its standard atomic weight is 87.62 u.
💡 Gives fireworks their scarlet red colour.
▶ Watch Strontium’s electrons orbit in the interactive periodic tableStrontium at a glance
| Symbol | Sr |
|---|---|
| Atomic number | 38 |
| Atomic mass | 87.62 u |
| Category | Alkaline earth metal |
| Group | 2 |
| Period | 5 |
| Block | s-block |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 5s2 |
| Noble-gas shorthand | [Kr] 5s2 |
| Electrons per shell | 2, 8, 18, 8, 2 |
| Outer-shell electrons | 2 |
| Electronegativity (Pauling) | 0.95 |
| State at 20 °C | solid |
| Flame test colour | scarlet red |
Where is Strontium on the periodic table?
Strontium is in period 5, group 2, in the s-block. The period number matches its 5 electron shells, and the block names the subshell its last electrons fill. In the same group, Calcium sits directly above it and Barium sits directly below it. Elements in one group have the same number of outer-shell electrons (2 here), which is why they react in similar ways.
How to work out the electron configuration of Strontium
Put 38 electrons into subshells in order of rising energy, filling each before starting the next: 1s² (2), 2s² (4), 2p⁶ (10), 3s² (12), 3p⁶ (18), 4s² (20), 3d¹⁰ (30), 4p⁶ (36), 5s² (38). In shorthand, [Kr] stands for the 36 electrons of krypton, giving [Kr] 5s².
How electronegative is Strontium?
Strontium has a Pauling electronegativity of 0.95, ranking 93 of the 100 elements with a known value (fluorine is highest at 3.98). That is low: it tends to give up electrons and form positive ions.
Strontium in the virtual lab
Faradium’s chemistry workbench includes these chemicals that contain strontium: Strontium chloride. Open the Chemistry Lab to experiment with them.
Frequently asked questions
What is the electron configuration of Strontium?
The electron configuration of Strontium (Sr) is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 5s2. In noble-gas shorthand it is written [Kr] 5s2.
How many electrons does Strontium have in each shell?
Strontium has 38 electrons arranged in shells as 2, 8, 18, 8, 2. It has 2 electrons in its outer shell.
What is the atomic mass of Strontium?
The standard atomic weight of Strontium is 87.62 u, so one mole of Strontium atoms has a mass of about 87.62 g.
Is Strontium a metal?
Yes. Strontium is an alkaline earth metal.
Explore nearby elements
More alkaline earth metals: Beryllium, Magnesium, Calcium, Barium, Radium. See all elements on the periodic table.