Symbol	He
Atomnummer	2
Gruppe	18 (Ædelgasser)
Periode	1
Blok	s
Klassifikation	Ædelgasser

Udseende	Colorless gas, exhibiting a red-orange glow when placed in a high-voltage electric field
Farve	Farveløs

Antal protoner	2 p+
Antal neutroner	2 n0
Antal elektroner	2 e-

Fra Wikipedia, den gratis encyklopædiHelium (af det græske ord for Solen; ἥλιος, helios) er det 2. grundstof i det periodiske system, og har det kemiske symbol He. Under normale tryk- og temperaturforhold optræder denne ædelgas som en farveløs, lugt- og smagsfri, enatomig, inaktiv og ugiftig gasart. Heliums koge- og smeltepunkter er de laveste blandt grundstofferne, og kun under ekstreme betingelser (højt tryk og lav temperatur) kan stoffet optræde som andet end en gas.

Fase ved STP	Gas
Massefylde	0.1786 g/cm3
Atommasse	4.0026 u

Smeltepunkt	0.95 K -272.2 °C -457.96 °F
Kogepunkt	4.222 K -268.928 °C -452.0704 °F
Fordampningsvarme	0.0845 kJ/mol

Elektronegativitet (Pauling Scale)	-
Elektronaffinitet	-48 kJ/mol
Oxidationstrin	0
Ioniseringsenergier	2372.3 kJ/mol 5250.5 kJ/mol

Elektronkonfiguration Kortfattet konfiguration	1s2
Elektronkonfiguration Fuld konfiguration	1s2
Elektronkonfigurationsdiagram	1s2
Elektroner pr. Skal	2
Valenselektroner	2
Valency-elektroner	0
Bohrs atommodel	Figur: Skaldiagram af Helium (He) atom.
Orbital diagram	1s

Opdaget	Pierre Janssen, Norman Lockyer (1868)
Første isolation	William Ramsay, Per Teodor Cleve, Abraham Langlet (1895)
Navngivet af	Edward Frankland, Norman Lockyer (1868)
Opdagelse af helium Helium was first detected as an unknown, yellow spectral line signature in sunlight during a solar eclipse in 1868 by Georges Rayet, Captain C. T. Haig, Norman R. Pogson, and Lieutenant John Herschel, and was subsequently confirmed by French astronomer Jules Janssen during a total solar eclipse in Guntur, India. Janssen is often jointly credited with detecting the element, along with Norman Lockyer. Janssen recorded the helium spectral line during the solar eclipse of 1868, while Lockyer observed it from Britain. Lockyer was the first to propose that the line was due to a new element. Lockyer and English chemist Edward Frankland named the element with the Greek word for the Sun, ἥλιος (helios). The formal discovery of the element was made in 1895 by chemists Sir William Ramsay, Per Teodor Cleve, and Nils Abraham Langlet, who found helium emanating from the uranium ore, cleveite, which is now not regarded as a separate mineral species, but as a variety of uraninite.

CAS Number	7440-59-7
ChemSpider ID	22423
EC number	231-168-5
PubChem CID Number	23987