Helium

2
He
Gruppe
18
Periode
1
Blok
s
Protons
Electrons
Neutrons
2
2
2
General Properties
Atomnummer
2
Atommasse
4,002602
Mass Number
4
Kategori
Ædelgasser
Farve
Colorless
Radioactive
Nej
From the Greek word helios, the sun
Krystalstruktur
Fladecentreret Kubisk
History
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 i hver skal
2
Elektronkonfiguration
1s2
He
Unlike any other element, helium will remain liquid down to absolute zero at normal pressures
Physical Properties
Tilstandsform
Gas
Massefylde
0,0001785 g/cm3
Smeltepunkt
0,95 K | -272,2 °C | -457,96 °F
Kogepunkt
4,22 K | -268,93 °C | -452,07 °F
Smeltevarme
0,02 kJ/mol
Fordampningsvarme
0,083 kJ/mol
Varmefylde
5,193 J/g·K
Abundance in Earth's crust
5,5×10-7%
Abundance in Universe
23%
Vial
Billede akkrediteringer: Images-of-elements
Vial of glowing ultrapure helium
CAS Number
7440-59-7
PubChem CID Number
23987
Atomic Properties
Atomradius
31 pm
Kovalent radius
28 pm
Elektronegativitet
-
Ionization Potential
24,5874 eV
Atomic Volume
27,2 cm3/mol
Varmeledningsevne
0,00152 W/cm·K
Oxidationstrin
0
Applications
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
Stable Isotopes
3He, 4He
Unstable Isotopes
5He, 6He, 7He, 8He, 9He, 10He