---
title: "Beryllium (Be): Atomic Mass, Electron Configuration & Properties"
url: https://www.moldraw.com/elements/beryllium.html
description: "Beryllium (Be), element 4: atomic mass 9.0122, electron configuration [He] 2s², group 2, period 2, s-block alkaline earth metal. Melting and boiling point, density, electronegativity and shells."
lang: en
publisher: Scidart Academy
generated: 2026-11-03
---
4Be9.0122

# Beryllium (Be) – element 4

Beryllium is a chemical element with the symbol **Be** and atomic number **4**. It is a alkaline earth metal in group 2 (alkaline earth metals), period 2 of the periodic table (s-block), and is a solid at room temperature.

Beryllium (Be) has atomic number 4, atomic mass 9.0122 u and electron configuration [He] 2s2.

[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)

## Beryllium facts

| Symbol | Be |
| --- | --- |
| Atomic number | 4 |
| Atomic mass | 9.0122 u (g/mol) |
| Category | alkaline earth metal |
| Group | group 2 (alkaline earth metals) |
| Period | 2 |
| Block | s-block |
| Phase at 20 °C | Solid |
| Electron configuration | 1s2 2s2 |
| Noble-gas notation | [He] 2s2 |
| Electrons per shell | 2, 2 |
| Valence electrons | 2 |

## Bohr model and shells

Beryllium has 4 electrons in 2 shells: 2, 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 | 1560 K (1286.8 °C) |
| --- | --- |
| Boiling point | 2742 K (2468.8 °C) |
| Density | 1.85 g/cm³ |
| Electronegativity (Pauling) | 1.57 |
| Electron affinity | -48 kJ/mol |
| Ionization energies | 899.5, 1757.1, 14848.7 kJ/mol (1st, 2nd, 3rd) |
| Molar heat capacity | 16.443 J/(mol·K) |
| Discovered by | Louis Nicolas Vauquelin |

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 Be.

## Position in the periodic table

Tap any element to open its page.

## Frequently asked questions

### What is the atomic mass of beryllium?

The atomic mass of beryllium is 9.0122 u, so one mole of beryllium atoms weighs 9.0122 g.

### What is the electron configuration of beryllium?

Beryllium has 4 electrons: 1s² 2s², or [He] 2s² in noble-gas notation. Electrons per shell: 2, 2.

### How many valence electrons does beryllium have?

Beryllium has 2 valence electrons (group 2).

### Is beryllium a metal?

Yes. Beryllium is a alkaline earth metal.

### Where is beryllium on the periodic table?

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