Helium

Document v1 · published by Koskamo · updated 2026-10-04

Helium (He) is chemical element 2, a noble gas in group 18, period 1 (PubChem).

Atomic number: 2
Symbol: He
Group: 18
Period: 1
Atomic mass: 4.00260 u
Electron configuration: 1s2
Atomic radius (van der Waals): 140 pm
Ionization energy: 24.587 eV
Oxidation states: 0
Standard state: Gas
Melting point: 0.95 K
Boiling point: 4.22 K
Density: 0.0001785 g/cm³
Chemical group: Noble gas
Year discovered: 1868

Source and provenance

Original source: pubchem.ncbi.nlm.nih.gov
Published on Koskamo by: Koskamo
Citation version: Document v1
Reuse: PubChem periodic table data (NIH/NLM, pubchem.ncbi.nlm.nih.gov/ptable); group and period from Jefferson Lab via PubChem

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Version history

Published by Koskamo2026-10-04
Version 1