Helium atom
 Helium-4 | |
| Names | |
|---|---|
| Systematic IUPAC name
Helium | |
| Identifiers | |
3D model (JSmol) |
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| ChEBI | |
| ChemSpider | |
| EC Number |
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| 16294 | |
| KEGG | |
| MeSH | Helium |
PubChem CID |
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| RTECS number |
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| UNII | |
| UN number | 1046 |
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| Properties | |
| He | |
| Molar mass | 4.002602 g·mol−1 |
| Appearance | Colourless gas |
| Boiling point | −269 °C (−452.20 °F; 4.15 K) |
| Thermochemistry | |
Std molar entropy (S⦵298) |
126.151-126.155 J K−1 mol−1 |
| Pharmacology | |
| V03AN03 (WHO) | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references | |
A helium atom is an atom of the chemical element helium. Helium is composed of two electrons bound by the electromagnetic force to a nucleus containing two protons along with two neutrons, depending on the isotope, held together by the strong force. Unlike for the hydrogen atom, a closed-form solution to the Schrödinger equation for the helium atom has not been found. However, various approximations, such as the Hartree–Fock method, can be used to estimate the ground state energy and wavefunction of the atom.
Historically, the first attempt to obtain the helium spectrum from quantum mechanics was done by Albrecht Unsöld in 1927. Egil Hylleraas obtained an accurate approximation in 1929. Its success was considered to be one of the earliest signs of validity of Schrödinger's wave mechanics.