---
title: "Barium (Ba): Atomic Mass, Electron Configuration & Properties"
url: https://www.moldraw.com/elements/barium.html
description: "Barium (Ba), element 56: atomic mass 137.33, electron configuration [Xe] 6s², group 2, period 6, s-block alkaline earth metal. Melting and boiling point, density, electronegativity and shells."
lang: en
publisher: Scidart Academy
generated: 2026-11-03
---
56Ba137.33

# Barium (Ba) – element 56

Barium is a chemical element with the symbol **Ba** and atomic number **56**. It is a alkaline earth metal in group 2 (alkaline earth metals), period 6 of the periodic table (s-block), and is a solid at room temperature.

Barium (Ba) has atomic number 56, atomic mass 137.33 u and electron configuration [Xe] 6s2.

[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)

## Barium facts

| Symbol | Ba |
| --- | --- |
| Atomic number | 56 |
| Atomic mass | 137.33 u (g/mol) |
| Category | alkaline earth metal |
| Group | group 2 (alkaline earth metals) |
| Period | 6 |
| Block | s-block |
| Phase at 20 °C | Solid |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 |
| Noble-gas notation | [Xe] 6s2 |
| Electrons per shell | 2, 8, 18, 18, 8, 2 |
| Valence electrons | 2 |

## Bohr model and shells

Barium has 56 electrons in 6 shells: 2, 8, 18, 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 | 1000 K (726.9 °C) |
| --- | --- |
| Boiling point | 2118 K (1844.8 °C) |
| Density | 3.51 g/cm³ |
| Electronegativity (Pauling) | 0.89 |
| Electron affinity | 13.954 kJ/mol |
| Ionization energies | 502.9, 965.2, 3600 kJ/mol (1st, 2nd, 3rd) |
| Molar heat capacity | 28.07 J/(mol·K) |
| Discovered by | Carl Wilhelm Scheele |

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 Ba.

## Position in the periodic table

Tap any element to open its page.

## Frequently asked questions

### What is the atomic mass of barium?

The atomic mass of barium is 137.33 u, so one mole of barium atoms weighs 137.33 g.

### What is the electron configuration of barium?

Barium has 56 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s², or [Xe] 6s² in noble-gas notation. Electrons per shell: 2, 8, 18, 18, 8, 2.

### How many valence electrons does barium have?

Barium has 2 valence electrons (group 2).

### Is barium a metal?

Yes. Barium is a alkaline earth metal.

### Where is barium on the periodic table?

Barium is in group 2 (alkaline earth metals), period 6, 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.