Nodyn:Infobox helium

hydrogen ← heliwm → lithiwm - ↑ He ↓ Ne 2He Y Tabl Cyfnodol
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	18, 1, 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
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.

References

These references will appear in the article, but this list appears only on this page.