Helium

2
He
Gruppe
18
Periode
1
Blokk
s
Protoner
Elektroner
Nøytroner
2
2
2
Generelle egenskaper
Atomnummer
2
Atomvekt
4,002602
Massetall
4
Kategori
Edelgasser
Farge
Fargeløs
Radioaktiv
Nei
From the Greek word helios, the sun
Krystallstruktur
Face Centered Cubic
Historie
French astronomer Jules Janssen obtained the first evidence of helium during the solar eclipse of 1868.

Norman Lockyer and Edward Frankland suggested the name helium for the new element.

In 1895, Sir William Ramsay discovered helium in the uranium mineral cleveite.

It was independently discovered in cleveite by Per Teodor Cleve and Abraham Langlet.
Elektroner per energinivå
2
Elektronkonfigurasjon
1s2
He
Unlike any other element, helium will remain liquid down to absolute zero at normal pressures
Fysikalske egenskaper
Fase
Gass
Tetthet
0,0001785 g/cm3
Smeltepunkt
0,95 K | -272,2 °C | -457,96 °F
Kokepunkt
4,22 K | -268,93 °C | -452,07 °F
Smeltevarme
0,02 kJ/mol
Fordampningsvarme
0,083 kJ/mol
Spesifikk varmekapasitet
5,193 J/g·K
Forekomst i jordskorpa
5,5×10-7%
Forekomst i universet
23%
Vial
Bildekreditter: Images-of-elements
Vial of glowing ultrapure helium
CAS Number
7440-59-7
PubChem CID Number
23987
Atomegenskaper
Atomradius
31 pm
Kovalent radius
28 pm
Elektronegativitet
-
Ioniseringsenergi
24,5874 eV
Molart volum
27,2 cm3/mol
Termisk ledningsevne
0,00152 W/cm·K
Oksidasjonstilstander
0
Bruksområder
Helium is used as a protective gas in growing silicon and germanium crystals, in titanium and zirconium production, and in gas chromatography.

Helium at low temperatures is used in cryogenics.

Helium is used for filling balloons and for pressurizing liquid fuel rockets.

Helium is used as a shielding gas in arc welding processes.
Helium is not known to be toxic
Isotoper
Stabile isotoper
3He, 4He
Ustabile isotoper
5He, 6He, 7He, 8He, 9He, 10He