Heli (He)

chemical element with symbol He and atomic number 2; rare gas

Atomic Number	2
Atomic Weight	4.002602
Rhif màs	4

Group	18
Period	1
Block	s

Proton	2 p⁺
Niwtron	2 n⁰
Electron	2 e^-

Nodwedd Ffisegol

Atomic Radius	120 pm 134 pm
molar volume	31.8 cm³/mol
covalent radius	46 pm 28 pm
Metallic Radius	122 pm
ionic radius
Crystal Radius
Van der Waals radius	140 pm 140 pm 153 pm 236.2 pm
density	0.000164 g/cm³

Nodwedd Gemegol

egni

proton affinity	177.8 kJ/mol
electron affinity	-19.7 eV/particle
ionization energy	24.587387936 eV/particle 54.41776311 eV/particle

enthalpy of vaporization	0.08 kJ/mol
enthalpy of fusion
standard enthalpy of formation
Electron

plisgyn yr electron	2

valence electron	2 ⓘ

trefn yr electronnau	1s²ⓘ

Cyflwr ocsidiad
Electronegatifedd	24.59 eV/particle 0.442712
Electrophilicity Index	0.0674191963846371 eV/particle
cyflwr sylfaenol mater

cyflwr mater	Gas
gaseous state of matter	Monoatomic
Boiling Point	4.222 K
Melting Point
critical pressure	0.22746 MPa
critical temperature	5.195 K
triple point	2.177 K 5.043 kPa
appearance
lliw	Colorless #ffc0cb #d9ffff #d9ffff
appearance	colorless gas, exhibiting a red-orange glow when placed in a high-voltage electric field
Mynegrif plygiant	1.000035
nodwedd ffisegol gwrthrych
Thermal Conductivity	0.152 W/(m K)
thermal expansion
molar heat capacity	20.786 J/(mol K)
Specific Heat Capacity	5.193 J/(g⋅K)
heat capacity ratio	5/3
electrical properties
type
dargludedd trydanol
Gwrthedd
superconductivity
magnetism
type	diamagnetic
magnetic susceptibility (Mass)	-0.0000000059 m³/Kg
magnetic susceptibility (Molar)	-0.0000000000236 m³/mol
magnetic susceptibility (Volume)	-0.00000000105
magnetic ordering
Curie temperature
Néel temperature
strwythur
Crystal Structure	Face Centered Cubic (HEX)
lattice constant	3.57 Å
Lattice Angles	π/2, π/2, π/2
nodwedd mecanyddol deunyddiau
hardness
bulk modulus
shear modulus
Young's modulus
Poisson's ratio
speed of sound	970 m/s
classification
Category	Noble gases, Noble gases
CAS Group	VIII
IUPAC Group	VIIIA
Glawe Number	1
Mendeleev Number	112
Pettifor Number	1
Geochemical Class	volatile
Goldschmidt classification	atmophile

other

Gas Basicity	148.5 kJ/mol
polarizability	1.38375 ± 0.00002 a₀
C6 Dispersion Coefficient	1.42 a₀ 1.47 a₀
allotrope
Neutron cross section	0.007
Neutron Mass Absorption	0.00001
quantum number	1S0
space group	225 (Fm_3m)

Isotopes of Helium

Stable Isotopes	2
Unstable Isotopes	6
Natural Isotopes	2

³He

Rhif màs	3
neutron number	1
Relative Atomic Mass	3.01602932197 ± 0.00000000006 Da
g-factor	-4.25525062 ± 0.00000006
natural abundance	0.0002 ± 0.0002
Dadfeilio ymbelydrol	stable isotope
Hanner oes	Not Radioactive ☢️
spin	1/2
nuclear quadrupole moment	0
dyddiad darganfod	1934
parity	+

⁴He

Rhif màs	4
neutron number	2
Relative Atomic Mass	4.00260325413 ± 0.00000000016 Da
g-factor	0
natural abundance	99.9998 ± 0.0002
Dadfeilio ymbelydrol	stable isotope
Hanner oes	Not Radioactive ☢️
spin	0
nuclear quadrupole moment	0
dyddiad darganfod	1908
parity	+

⁵He

Rhif màs	5
neutron number	3
Relative Atomic Mass	5.012057224 ± 0.00002147 Da
g-factor
natural abundance
Dadfeilio ymbelydrol	☢️ elfen ymbelydrol
Hanner oes	602 ± 22 ys
spin	3/2
nuclear quadrupole moment
dyddiad darganfod	1937
parity	-

decay mode	intensity
n (neutron emission)	100%

⁶He

Rhif màs	6
neutron number	4
Relative Atomic Mass	6.018885889 ± 0.000000057 Da
g-factor	0
natural abundance
Dadfeilio ymbelydrol	☢️ elfen ymbelydrol
Hanner oes	806.92 ± 0.24 ms
spin	0
nuclear quadrupole moment	0
dyddiad darganfod	1936
parity	+

decay mode	intensity
β⁻ (β⁻ decay)	100%
β⁻ d (β⁻-delayed deuteron emission)	0.000278%

⁷He

Rhif màs	7
neutron number	5
Relative Atomic Mass	7.027990652 ± 0.000008115 Da
g-factor
natural abundance
Dadfeilio ymbelydrol	☢️ elfen ymbelydrol
Hanner oes	2.51 ± 0.07 zs
spin	3/2
nuclear quadrupole moment
dyddiad darganfod	1967
parity

decay mode	intensity
n (neutron emission)	100%

⁸He

Rhif màs	8
neutron number	6
Relative Atomic Mass	8.033934388 ± 0.000000095 Da
g-factor	0
natural abundance
Dadfeilio ymbelydrol	☢️ elfen ymbelydrol
Hanner oes	119.5 ± 1.5 ms
spin	0
nuclear quadrupole moment	0
dyddiad darganfod	1965
parity	+

decay mode	intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	16%
β⁻ t (β⁻-delayed triton emission)	0.9%

⁹He

Rhif màs	9
neutron number	7
Relative Atomic Mass	9.043946414 ± 0.000050259 Da
g-factor
natural abundance
Dadfeilio ymbelydrol	☢️ elfen ymbelydrol
Hanner oes	2.5 ± 2.3 zs
spin	1/2
nuclear quadrupole moment	0
dyddiad darganfod	1987
parity

decay mode	intensity
n (neutron emission)	100%

¹⁰He

Rhif màs	10
neutron number	8
Relative Atomic Mass	10.052815306 ± 0.000099676 Da
g-factor	0
natural abundance
Dadfeilio ymbelydrol	☢️ elfen ymbelydrol
Hanner oes	260 ± 40 ys
spin	0
nuclear quadrupole moment	0
dyddiad darganfod	1994
parity	+

decay mode	intensity
2n (2-neutron emission)	100%

hanes

darganfyddwr neu ddyfeisiwr	Sir William Ramsey, Nils Langet, P.T.Cleve
man darganfod	Scotland/Sweden
dyddiad darganfod	1895
geirdarddiad	Greek: hêlios (sun).
ynganiad	HEE-li-em (Saesneg)

source

Abundance
Abundance in Earth's crust	0.008 mg/kg
natural abundance (cefnfor)	0.000007 mg/L
natural abundance (corff dynol)
natural abundance (Awyrfaen)
natural abundance (Haul)	23 %
Abundance in Universe	23 %

Nuclear Screening Constants

0.3125

Heli on ChemicalAid

Australian Educational Vocabulary ID	scot/3528
Brockhaus Enzyklopädie online ID	helium-20
CAB ID	178029
ChEBI ID	30217
ChEMBL ID	CHEMBL1796997
ChemSpider ID	22423
Cod yr ATC	V03AN03
Common Procurement Vocabulary	24111300
DSSTOX compound identifier	DTXCID5016402
DSSTox substance ID	DTXSID7036402
De Agostini ID	èlio
Den Store Danske ID	helium
Dynodwr Drugbank (Alberta)	09155
ECHA Substance Infocard ID	100.028.334
French Vikidia ID	Hélium
GND	4132459-6
Golden ID	Helium-K8NB
Great Russian Encyclopedia Online ID	2348591
ID NALT	44987
InChI	InChI=1S/He
InChIKey	SWQJXJOGLNCZEY-UHFFFAOYSA-N
Italian Vikidia ID	Elio
Krugosvet article	nauka_i_tehnika/himiya/GELI.html
Mindat mineral ID	25563
NDF-RT	N0000147379
Namuwiki ID	헬륨
National Library of Israel J9U ID	987007555644805171
OmegaWiki Defined Meaning	7296
Online PWN Encyclopedia ID	3910758
OpenAlex ID	C546029482
OpenAlex ID	C2991909631
Probes And Drugs ID	PD009020
PubChem CID	23987
Rhif Cofrestru CAS	7440-59-7
RxNorm ID	5140
Römpp online ID	RD-08-00783
Spanish Vikidia ID	Helio
Store norske leksikon ID	helium
UMLS CUI	C0018880
UNII	206GF3GB41
USGS Thesaurus ID	1470
WordNet 3.1 Synset ID	14664099-n
World of Physics ID	Helium
ZVG number	7020
dynodwr Archifau Cenedlaethol yr Unol Daleithiau	10640583
dynodwr BnF	11978648w
dynodwr Encyclopædia Britannica Online	science/helium-chemical-element
dynodwr Encyclopædia Universalis	helium
dynodwr Freebase	/m/025rt79
dynodwr HSDB	553
dynodwr ICSC	0603
dynodwr KBpedia	Helium
dynodwr Klexikon (erthygl)	Helium
dynodwr LCAuth	sh85060043
dynodwr MeSH	D006371
dynodwr NDL	00563132
dynodwr NE.se	helium
dynodwr NKC	ph503003
dynodwr PSH	5816
dynodwr Quora	Helium
dynodwr Treccani	elio
dynodwr YSO	14499
dynodwr yn thesawrws y BNCF	19752
rhif E	E939

Heli (He)

Nodwedd Ffisegol

Nodwedd Gemegol

other

Isotopes of Helium

3He

4He

5He

6He

7He

8He

9He

10He

hanes

source

Nuclear Screening Constants

³He

⁴He

⁵He

⁶He

⁷He

⁸He

⁹He

¹⁰He