---
title: "Strontium (Sr) — element 38"
description: "Strontium is element 38, symbol Sr, atomic weight 87.62. Configuration, properties, uses and neighbours."
url: https://atoneplace.net/element/strontium/
site: "At One Place"
---

# Strontium (Sr)

**Strontium — element 38: Sr**

87.62 u · Alkaline earth metal · period 5, group 2

Strontium behaves chemically like calcium, which is the whole problem with strontium-90: fallout from atmospheric nuclear testing was taken up into bone and teeth as if it were calcium, and the "baby tooth survey" of the early 1960s measured it in children's milk teeth well enough to help push through the Partial Test Ban Treaty. That same chemistry makes it useful — strontium ions substituting into bone mineral is why it was prescribed for osteoporosis. Strontium salts give the purest red in pyrotechnics; nothing else comes close.

## Properties

- **Atomic number:** 38
- **Symbol:** Sr
- **Standard atomic weight:** 87.62 u
- **Category:** Alkaline earth metal
- **Group:** 2
- **Period:** 5
- **Block:** s-block
- **Electron configuration:** [Kr] 5s²
- **Electrons per shell:** 2, 8, 18, 8, 2
- **Melting point:** 1,050 K — 776.9 °C — 1430.3 °F
- **Boiling point:** 1,655 K — 1381.8 °C — 2519.3 °F
- **Density:** 2.64 g/cm³
- **Electronegativity:** 0.95 (Pauling)
- **Oxidation states:** +2
- **Discovered:** 1790 by Adair Crawford; isolated by Humphry Davy in 1808

## Electron configuration

- **Full:** 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s²
- **Noble gas shorthand:** [Kr] 5s²
- **Shells:** K: 2 · L: 8 · M: 18 · N: 8 · O: 2

## What it is used for

- The red in fireworks, road flares and tracer rounds
- Strontium ranelate for osteoporosis, in some countries
- Strontium aluminate in glow-in-the-dark paint and exit signs
- Strontium-90 as a heat source in remote thermoelectric generators
- Ferrite magnets in loudspeakers and small motors

## Hazards

- Strontium-90 is a bone-seeking beta emitter with a 28.8-year half-life

> Named after Strontian, a village in the Scottish Highlands where the mineral strontianite was found — the only chemical element named after a place in the British Isles.

## Neighbours in the table

| Z | Element | Symbol | Mass |
| --- | --- | --- | --- |
| 36 | Krypton | Kr | 83.798 |
| 37 | Rubidium | Rb | 85.468 |
| 38 | Strontium ← | Sr | 87.62 |
| 39 | Yttrium | Y | 88.906 |
| 40 | Zirconium | Zr | 91.222 |

## Group 2

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Strontium sits in group 2 with beryllium, magnesium, calcium, barium, radium.

## Common questions

### What is the atomic number of strontium?

38. That is the number of protons in its nucleus, which is what defines the element.

### What is the symbol for strontium?

Sr.

### What is the electron configuration of strontium?

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s², or [Kr] 5s² in noble-gas shorthand.

### What is the melting point of strontium?

1,050 K — 776.9 °C — 1430.3 °F

## Related pages

- [Krypton (Kr)](https://atoneplace.net/element/krypton/)
- [Rubidium (Rb)](https://atoneplace.net/element/rubidium/)
- [Yttrium (Y)](https://atoneplace.net/element/yttrium/)
- [Zirconium (Zr)](https://atoneplace.net/element/zirconium/)
- [Beryllium (Be)](https://atoneplace.net/element/beryllium/)
- [Magnesium (Mg)](https://atoneplace.net/element/magnesium/)
- [Calcium (Ca)](https://atoneplace.net/element/calcium/)
- [Barium (Ba)](https://atoneplace.net/element/barium/)
- [Radium (Ra)](https://atoneplace.net/element/radium/)

## Sources

- Official vendor product documentation — At One Place (/about/)