Helium is a light, exceptionally unreactive gas. Its usefulness extends far beyond balloons: it cools superconducting magnets in scientific instruments and medical scanners. It also supplies protective atmospheres where unwanted chemical reactions would interfere with making materials such as optical fibers.
FROM ELEMENT TO APPLICATION
AN ELEMENT IN CONTEXT
Why can liquid helium enable a magnet without producing its magnetic field?
Liquid helium
FOLLOW THIS RELATIONSHIP
Identify the temperature requirement
A superconducting magnet uses a material whose operating state requires sufficiently low temperature; the required conditions belong to that magnet system.
Explore the model (optional)
HeFORM → INTERACTION → CONSEQUENCE
Follow the explanation in either direction. These are authored steps, not a physical clock.
Atomic identity, reference properties and structure models
INTERACTIVE 3D2 visible sites
An electron censusDrag to rotate · scroll or pinch to zoom
1s2. Grouping electrons by principal shell connects the neutral-atom configuration to periodic-table patterns.
What this representation means
A three-dimensional counting diagram. Dots are count markers, not measured electron positions; spherical placement and spacing are arbitrary. There are no electron trajectories here. Orbitals describe quantum states.
Helium first entered science as an unfamiliar line in the solar , observed in 1868 by Janssen and independently by Lockyer. The clue preceded the isolation of a terrestrial sample. In 1895, Ramsay and Swedish researchers working independently identified helium released from . Its history demonstrates that an element can be inferred through light before its presence in a laboratory sample is established.
1868
Solar spectral evidence
Janssen and Lockyer observed a previously unexplained solar spectral line.
1895
Terrestrial helium isolated
Ramsay and, independently, Cleve and Langlet identified helium from minerals.
Helium occurs in stars and in some natural-gas deposits from which it is extracted. On Earth, radioactive also produces helium that may accumulate underground or escape. Atmospheric helium is dilute, so recognizing an element as widespread does not mean every reservoir is a practical source.
Helium has very low chemical reactivity and becomes liquid only at extremely low temperature. At ordinary pressure, cooling alone does not make it solid; pressure also matters. Its behavior illustrates the difference between chemical inertness, which concerns reactions, and behavior, which depends on physical conditions.
Each section links its supporting references. Descriptions and diagrams were authored for this atlas. Source checks completed. Source checks dated 2026-09-06.
CITE THIS PAGE
Family labels and the group-3 layout are teaching conventions. A table position does not establish an unknown bulk property. Electronic configurations refer to neutral atoms; ions and material environments require their own account.
Read each reference property together with its units, conditions and the reference information below.
Not yet recorded: electron affinity, second ionization energy, ground-state term symbol, van der waals radius, thermal conductivity, specific heat capacity, electrical resistivity, crystal structure, lattice parameter a, space group, abundance in seawater, abundance in the universe, annual production, supply-risk listing, hazard classification, biological role, cas registry number, pubchem cid, wikidata item. These families are declared and awaiting an ingestion run against the source each names; they are listed here rather than shown as empty rows.
Physical
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Phase at 20 °C
gas
293.15 K, 101.325 kPa
Melting point
Not recorded
at standard pressure unless noted
Boiling point in K
4.22 K
101.325 kPa
Density in g/cm³
0.000179 g/cm³
solids and liquids at 293 K; gases at 273 K and 101.325 kPa
Atomic and electronic
Intended reference: Pauling electronegativity scale · Widely tabulated; original in The Nature of the Chemical Bond
Electronegativity
Not recorded
Pauling scale
First ionization energy in kJ/mol
2372 kJ/mol
gas-phase neutral atom, ground state
Covalent radius in pm
28 pm
single-bond covalent radius
Common oxidation states
0
states met in ordinary compounds; not exhaustive
Occurrence and identity
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Abundance in the crust in mg/kg
0.008 mg/kg
upper continental crust, mass fraction
Has stable isotopes
Yesderived
Discovery year in CE
1868 CEderived
WHERE IT SITS AMONG ITS NEIGHBORS
Electronegativity down group 18
Kr 3 Pauling · Krypton
Electronegativity down group 18. Exact values.
Kr
3
Xe
2.6
The trend uses the same reference-property values as the periodic table. Elements with no recorded value are left out of the line rather than drawn at zero.
