Helium

2
He
Grupp
18
Period
1
Block
s
Protoner
Elektroner
Neutroner
2
2
2
Generella Egenskaper
Atomnummer
2
Atommassa
4,002602
Masstal
4
Kategori
Ädelgaser
Färg
Färglös
Radioaktiv
Nej
From the Greek word helios, the sun
Kristallstruktur
Ytcentrerat kubiskt
Historia
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 skal
2
Elektronkonfiguration
1s2
He
Unlike any other element, helium will remain liquid down to absolute zero at normal pressures
Fysikaliska Egenskaper
Aggregationstillstånd
Gasformig
Densitet
0,0001785 g/cm3
Smältpunkt
0,95 K | -272,2 °C | -457,96 °F
Kokpunkt
4,22 K | -268,93 °C | -452,07 °F
Smältvärme
0,02 kJ/mol
Ångbildningsvärme
0,083 kJ/mol
Specifik värmekapacitet
5,193 J/g·K
Abundance in Earth's crust
5,5×10-7%
Abundance in Universe
23%
Vial
Bildkrediter: Images-of-elements
Vial of glowing ultrapure helium
CAS Number
7440-59-7
PubChem CID Number
23987
Atomära Egenskaper
Atomradie
31 pm
Kovalent radie
28 pm
Elektronegativitet
-
Jonisationspotential
24,5874 eV
Molvolym
27,2 cm3/mol
Värmeledningsförmåga
0,00152 W/cm·K
Oxidationstillstånd
0
Användningsområden
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
Stabila isotoper
3He, 4He
Instabila isotoper
5He, 6He, 7He, 8He, 9He, 10He