Helium

An element / simple molecule, He, 4.003 g/mol. Boiling point -268.928 °C, melting point -272.2, as published.

verified recordElement / simple molecule5 measured properties

Identifiers

Molecular formula: He
Molecular weight: 4.003 g/mol
Exact mass: 4.002603 g/mol
IUPAC name: helium
SMILES: [He]
InChI: InChI=1S/He
InChIKey: SWQJXJOGLNCZEY-UHFFFAOYSA-N

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Measured properties

Published measurements, each with its source. Two readings of one property are both shown, in the units each used.

Boiling Point: -269measured · DrugBank; -268.928 °Cmeasured · Hazardous Substances Data Bank (HSDB)
Melting Point: -272.2measured · DrugBank; No triple pointmeasured · Hazardous Substances Data Bank (HSDB)
Density: 1.64 g/Lmeasured · Hazardous Substances Data Bank (HSDB); Liquid helium has unique thermodynamic properties ... Refractive index 1,026, density 0.125 and is called a "quantum fluid" because it exhibits atomic properties on a macroscopic scale. Its BP is nearmeasured · Hazardous Substances Data Bank (HSDB)
Solubility: 1.5mg/Lmeasured · DrugBank; Very slightly soluble in water: at 0 °C, 0.97 mL/100 mL; at 50 °C, 1.08 mL/100 mLmeasured · Hazardous Substances Data Bank (HSDB)
LogP: 0.28measured · DrugBank; 0.28measured · Human Metabolome Database (HMDB)

Calculated properties

Derived from the structure, not from a sample; kept apart from the measurements above.

Molecular weight: 4.0026 g/molcalculated · reference compound database; Average mass of one molecule, from reference compound database.
Exact mass: 4.002603254 Dacalculated · reference compound database; Mass of the most common isotopic form.
Polar surface area: 0 Å²calculated · reference compound database; Polar surface area as computed by reference compound database.
Complexity: 0calculated · reference compound database; A rough measure of how intricate the structure is.
H-bond donors: 0calculated · reference compound database
H-bond acceptors: 0calculated · reference compound database
logP: 0calculated · chemistry engine; Estimated preference for oil over water. Higher means more oil-like.
Topological polar surface area: 0 Å²calculated · chemistry engine; Surface area from polar atoms; relates to how easily a molecule crosses membranes.
H-bond donors: 0calculated · chemistry engine; Atoms that can donate a hydrogen bond.
H-bond acceptors: 0calculated · chemistry engine; Atoms that can accept a hydrogen bond.
Rotatable bonds: 0calculated · chemistry engine; Single bonds the molecule can freely twist around.
Molar refractivity: 0 cm³/molcalculated · chemistry engine; Relates to the molecule's polarisability.
Fraction sp³ carbons: 0calculated · chemistry engine; Share of carbon atoms with tetrahedral bonding.
QED drug-likeness: 0.3407calculated · chemistry engine; Quantitative estimate of drug-likeness (0–1).

What it is made of

Elements

He Helium1 atom · 100.0% by mass

Percentages are of the molecular weight above, worked out the same way the molar mass calculator does it.

Structure

Heavy atoms, hydrogen excluded: 1
Total atoms, hydrogen included: 1
Rings: 0
Aromatic rings: 0
Stereocentres: 0
Formal charge: 0

The molecule in three dimensions

Rotate and inspect the atoms. Loaded only when you ask, so the page stays light.

The drawing above is a diagram of what is bonded to what. A molecule is not flat, and the model here is one low-energy shape generated from the connectivity — useful for seeing which groups can reach each other, and not a measured structure. A real sample is a population of conformations, interconverting.

Reactions it appears in

No documented reaction with a written procedure and a source involves Helium yet.

Other names for it

The systematic name on this record is helium.

The sources also call it Atomic helium, Helium-4, p-Helium, O-Helium, Helium (USP), Helium 4, Helium [USP].

Structurally related

Nothing structurally close to Helium has a page here yet.

Where these values came from

reference compound database23987
compound record
chemistry engine
structure perception

compound record.

What this page does not claim

Identifiers are copied from the source record, measured values are reported as published, and calculated values are marked as calculated. Nothing here is a hazard, purity or handling assessment — how the library is checked.