---
title: "Helium (He): Atomic Mass, Electron Configuration & Properties"
url: https://www.moldraw.com/elements/helium.html
description: "Helium (He), element 2: atomic mass 4.0026, electron configuration 1s², group 18, period 1, s-block noble gas. Melting and boiling point, density, electronegativity and shells."
lang: en
publisher: Scidart Academy
generated: 2026-11-03
---
2He4.0026

# Helium (He) – element 2

Helium is a chemical element with the symbol **He** and atomic number **2**. It is a noble gas in group 18 (noble gases), period 1 of the periodic table (s-block), and is a gas at room temperature.

Helium (He) has atomic number 2, atomic mass 4.0026 u and electron configuration 1s2.

[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)

## Helium facts

| Symbol | He |
| --- | --- |
| Atomic number | 2 |
| Atomic mass | 4.0026 u (g/mol) |
| Category | noble gas |
| Group | group 18 (noble gases) |
| Period | 1 |
| Block | s-block |
| Phase at 20 °C | Gas |
| Electron configuration | 1s2 |
| Noble-gas notation | 1s2 |
| Electrons per shell | 2 |
| Valence electrons | 2 |

## Bohr model and shells

Helium has 2 electrons in 1 shell: 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 | 0.95 K (-272.2 °C) |
| --- | --- |
| Boiling point | 4.222 K (-268.9 °C) |
| Density | 0.1786 g/L |
| Electron affinity | -48 kJ/mol |
| Ionization energies | 2372.3, 5250.5 kJ/mol (1st, 2nd) |
| Discovered by | Pierre Janssen |

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 He.

## Position in the periodic table

Tap any element to open its page.

## Frequently asked questions

### What is the atomic mass of helium?

The atomic mass of helium is 4.0026 u, so one mole of helium atoms weighs 4.0026 g.

### What is the electron configuration of helium?

Helium has 2 electrons: 1s², or 1s² in noble-gas notation. Electrons per shell: 2.

### How many valence electrons does helium have?

Helium has 2 valence electrons (group 18).

### Is helium a metal?

No. Helium is a nonmetal (noble gas).

### Where is helium on the periodic table?

Helium is in group 18 (noble gases), period 1, 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.