Nodyn:Infobox helium

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hydrogenheliwmlithiwm
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He

Ne
Ymddangosiad
Nwy diliw, er bod iddo wawr orengoch pan rhoddir ef mewn maes trydan foltedd uchel.


Llinellau sbectral heliwm
Nodweddion cyffredinol
Enw, symbol, rhif heliwm, He, 2
Teulu'r elfennau nwy nobl
Grŵp, cyfnod, bloc 181, s
Rhif atomig 4.002602(2)
Patrwm yr Electronnau 1s2
Electronnau / cragen 2 (Image)
Nodweddion ffisegol
Stâd nwy
Dwysedd (0 °C, 101.325 kPa)
0.1786 g/L
Dwysedd hylif / Ymdoddbwynt 0.145 g·cm−3
Ymdoddbwynt (at 2.5 MPa) 0.95 K, −272.20 °C, −457.96 °F
Berwbwynt 4.22 K, −268.93 °C, −452.07 °F
Pwynt critigol 5.19 K, 0.227 MPa
Enthalpi ymdoddiad

Gwres o ymdoddi

{{{heat fusion 2}}} kJ·mol−1
Enthalpi anweddiad Cynhwysedd gwres 5R/2 = 20.786 J·mol−1·K−1
Vapor pressure (defined by ITS-90)
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K)     1.23 1.67 2.48 4.21
Nodweddion Atomig
Electronegativity dim data (Graddfa Pauling)
egni ïoneiddiadau 1af: 2372.3 kJ·mol−1
2: 5250.5 kJ·mol−1
Radiws cofalent 28 pm
Radiws Van der Waals 140 pm
Amrywiol
Strwythyr y crisal hexagonal close-packed
Magnetic ordering diamagnetic[1]
Dargludiad Thermal 0.1513 W·m−1·K−1
Cyflymder sain 972 m·s−1
CAS registry number 7440-59-7
Most stable isotopes
Main article: Isotopes of heliwm
iso NA half-life DM DE (MeV) DP
3He 0.000137%* 3He is stable with 1 neutrons
4He 99.999863%* 4He is stable with 2 neutrons
*Atmospheric value, abundance may differ elsewhere.
· r

References

  1. Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics 81st edition, CRC press.