ELEMENTLE

Element 2 · Noble Gas

Helium

Period 1 · Group 18

Helium is a chemical element with symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table. Its boiling and melting points are the lowest among all the elements.

Three reasons Helium stands out

  1. 1

    Makes your voice go squeaky.

  2. 2

    It was discovered in the Sun before it was ever found on Earth.

  3. 3

    The only element that stays liquid all the way down to absolute zero at normal pressure.

A gas born before the stars

Most helium formed during the universe’s first few minutes, long before planets existed. Its closed electron shell makes it reluctant to react, while its exceptionally low boiling point keeps it liquid in machines that need extreme cold. Once released, its light atoms can eventually escape Earth altogether.

Helium at a glance
Atomic number / protons2
SymbolHe
Family (Elementle)Noble Gas
Classification (PubChem)Noble gas
Period1
Group18
Atomic mass (u)4.00260
Standard stateGas
Electron configuration1s2
Reported oxidation states0
Electronegativity (Pauling)Not available
Atomic radius (pm)140
First ionization energy (eV)24.587
Electron affinity (eV)Not available
Density (g/cm³)0.0001785
Melting pointRequires pressure; no melting point at 1 atm
Boiling point4.22 K (-268.93 °C)
Discovery (PubChem)1868

Values are reference data, not a specification for every temperature, pressure, or allotrope. Unknown properties are left unavailable. Superheavy-element predictions remain uncertain.

Sources & further reading

PubChem: Helium · Helium on Wikipedia

The introduction and original editorial story are adapted from Wikipedia contributors via Periodic-Table-JSON. Element descriptions and their adaptations are available under CC BY-SA 3.0. Numerical attributes use the PubChem periodic-table dataset, retrieved September 22, 2026.