Strontium (Sr)
Alkaline earth metal
Strontium burns with a brilliant crimson flame — the red in fireworks and signal flares. Chemically similar to calcium, it slots into bone mineral, which made its radioactive isotope from nuclear fallout a serious health concern.
Position on the periodic table
Atomic properties
| Atomic number | 38 |
|---|---|
| Atomic mass | 87.621 amu |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 |
| Noble gas shorthand | [Kr] 5s2 |
| Electrons per shell | 2, 8, 18, 8, 2 |
| Valence electrons (outer shell) | 2 |
| Common oxidation states | +2 |
| Electronegativity (Pauling) | 0.95 |
| Covalent radius (approx.) | 195 pm |
| First ionization energy | 549.5 kJ/mol |
| Electron affinity | 5 kJ/mol |
Physical properties
| State at 25 °C | Solid |
|---|---|
| Density | 2.64 g/cm³ |
| Melting point | 776.85 °C (1050 K) |
| Boiling point | 1376.8 °C (1650 K) |
| Appearance | Not available |
| Radioactive | No |
| Origin | Occurs naturally |
Electron configuration of strontium
Strontium's ground-state electron configuration is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2, usually shortened to [Kr] 5s2. Its electrons occupy 5 shells (2, 8, 18, 8, 2), placing it in period 5 of the s-block. The 2 outer-shell electrons drive its bonding behaviour. Explore it interactively in the electron configuration calculator.
Uses of strontium
- Red fireworks and flares
- Ferrite ceramic magnets
- Glow-in-the-dark paints (strontium aluminate)
- Some toothpastes for sensitive teeth
Biological role: Not essential, but strontium follows calcium into bones.
Occurrence: Mined as celestine and strontianite.
Common compounds of strontium
SrCO3
Strontium carbonate
Sr(NO3)2
Strontium nitrate
History and discovery
Discovered: 1790 — William Cruickshank (chemist). Name origin: Named after Strontian, the Scottish village where its mineral was found.
Recognised in 1790 by Adair Crawford; Humphry Davy isolated the metal in 1808.
Safety notes
Ordinary strontium is low-risk; radioactive strontium-90 from fallout is dangerous because it lodges in bone.
Educational context only — always follow your school's laboratory rules and never handle chemicals without proper supervision. See our disclaimer.
Practice questions
Quick practice: Strontium
1. What is the chemical symbol of Strontium?
2. What is the atomic number of Strontium?
3. Which category does Strontium belong to?
4. What is the state of Strontium at room temperature?
5. Which period of the periodic table is Strontium in?
Strontium FAQs
What is the atomic number of strontium?
Strontium's atomic number is 38 — every strontium atom has 38 protons in its nucleus.
What is the symbol for strontium?
Sr. Named after Strontian, the Scottish village where its mineral was found.
Is strontium a metal, nonmetal, or metalloid?
Strontium is classified as a alkaline earth metal.
What state is strontium at room temperature?
At about 25 °C, strontium is a solid. It melts at 776.85 °C.
How many valence electrons does strontium have?
Strontium has 2 electrons in its outer shell (shell pattern: 2, 8, 18, 8, 2).
What is strontium used for?
Key uses include: red fireworks and flares; ferrite ceramic magnets; glow-in-the-dark paints (strontium aluminate).
Related elements
Keep working with this element
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