 Helium-4
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| Names | |
|---|---|
| Systematic IUPAC name
Helium[1] | |
| 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).
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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 hydrogen, 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 such helium spectrum calculation was done by Albrecht Unsöld in 1927.[2] Its success was considered to be one of the earliest signs of validity of Schrödinger's wave mechanics.[3]
- ^ "Helium - PubChem Public Chemical Database". The PubChem Project. USA: National Center for Biotechnology Information.
- ^ Unsöld, Ann. Phys., 82 (1927) 355
- ^ Sakurai, J. J.; Napolitano, Jim (2017-09-21). Modern Quantum Mechanics. Cambridge University Press. pp. 455–459. doi:10.1017/9781108499996. ISBN 978-1-108-49999-6.