Helium

Kemiallinen merkki: He
Järjestysluku: 2
Kategoria: jalokaasut
Ryhmä: 18
Jakso: 1
Lohko: s
Moolimassa: 4,002602 g/mol
Elektronia kuorilla: 2
CAS-numero: 7440-59-7
Olomuoto: kaasu
Tiheys: 0,1786 g/l (0 °C, 101,325 kPa)
Sulamispiste: 0,95 K (-272,20 °C, -457,96 °F) (at 2,5 MPa)
Kiehumispiste: 4,22 K (-268,93 °C, -452,07 °F)
Kiderakenne: hexagonal close-packed
Hapetusluvut: 0
Elektronegatiivisuus: unknown
Nimen alkuperä: Helios
Nimen tarkoitus: the Greek name for Sun because the discoverer concluded this element is found in the Sun
Faktoja:
- is a colorless, odorless, tasteless, non-toxic, inert monatomic gas
- its boiling and melting points are the lowest among the elements and it exists only as a gas except in extreme conditions
- is used in cryogenics, in deep-sea breathing systems, to cool superconducting magnets, in helium dating, for inflating balloons, for providing lift in airships and as a protective gas for many industrial uses
- inhaling a small volume of the gas temporarily changes the timbre and quality of the human voice
- is the second lightest element and is the second most abundant in the observable Universe
- most helium was formed during the Big Bang, but new helium is being created as a result of the nuclear fusion of hydrogen in stars
- has two liquid states - helium I and helium II - helium II is a superfluid
- at standard conditions is non-toxic, plays no biological role and is found in trace amounts in human blood - if enough helium is inhaled that oxygen needed for normal respiration is replaced asphyxia is possible