---
title: "Strontium (Sr): Atomic Mass, Electron Configuration & Properties"
url: https://www.moldraw.com/elements/strontium.html
description: "Strontium (Sr), element 38: atomic mass 87.62, electron configuration [Kr] 5s², group 2, period 5, s-block alkaline earth metal. Melting and boiling point, density, electronegativity and shells."
lang: en
publisher: Scidart Academy
generated: 2026-11-03
---
38Sr87.62

# Strontium (Sr) – element 38

Strontium is a chemical element with the symbol **Sr** and atomic number **38**. It is a alkaline earth metal in group 2 (alkaline earth metals), period 5 of the periodic table (s-block), and is a solid at room temperature.

Strontium (Sr) has atomic number 38, atomic mass 87.62 u and electron configuration [Kr] 5s2.

[Download periodic table PDF](https://www.moldraw.com/printables/periodic-table.pdf)[Open interactive periodic table](https://www.moldraw.com/tools/free-chem-tools/interactive-periodic-table.html)

## Strontium facts

| Symbol | Sr |
| --- | --- |
| Atomic number | 38 |
| Atomic mass | 87.62 u (g/mol) |
| Category | alkaline earth metal |
| Group | group 2 (alkaline earth metals) |
| Period | 5 |
| Block | s-block |
| Phase at 20 °C | Solid |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 |
| Noble-gas notation | [Kr] 5s2 |
| Electrons per shell | 2, 8, 18, 8, 2 |
| Valence electrons | 2 |

## Bohr model and shells

Strontium has 38 electrons in 5 shells: 2, 8, 18, 8, 2. Full configuration and noble-gas notation are in the table; work out any element or ion with the [electron configuration calculator](https://www.moldraw.com/tools/free-chem-tools/electron-configuration-calculator.html).

## Physical and atomic properties

| Melting point | 1050 K (776.9 °C) |
| --- | --- |
| Boiling point | 1650 K (1376.8 °C) |
| Density | 2.64 g/cm³ |
| Electronegativity (Pauling) | 0.95 |
| Electron affinity | 5.023 kJ/mol |
| Ionization energies | 549.5, 1064.2, 4138 kJ/mol (1st, 2nd, 3rd) |
| Molar heat capacity | 26.4 J/(mol·K) |
| Discovered by | William Cruickshank (chemist) |

Use the atomic mass in the [molar mass calculator](https://www.moldraw.com/tools/free-chem-tools/molar-mass-calculator.html) for any formula containing Sr.

## Position in the periodic table

Tap any element to open its page.

## Frequently asked questions

### What is the atomic mass of strontium?

The atomic mass of strontium is 87.62 u, so one mole of strontium atoms weighs 87.62 g.

### What is the electron configuration of strontium?

Strontium has 38 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s², or [Kr] 5s² in noble-gas notation. Electrons per shell: 2, 8, 18, 8, 2.

### How many valence electrons does strontium have?

Strontium has 2 valence electrons (group 2).

### Is strontium a metal?

Yes. Strontium is a alkaline earth metal.

### Where is strontium on the periodic table?

Strontium is in group 2 (alkaline earth metals), period 5, in the s-block.

Data: [Periodic-Table-JSON](https://github.com/Bowserinator/Periodic-Table-JSON) (CC BY-SA 3.0); standard atomic weights from IUPAC (abridged). Values in brackets are the mass number of the longest-lived isotope.