| Symbol | He |
| Atomic Number | 2
Noble gas |
Relative Atomic Mass
12C = 12.0000 | 4.002602 |
| Atomic Radius pm | 32 |
First Ionisation Energy
kJ mol -1 | 2372.3 |
| Ionization energy (eV) | 24,5874 |
| Electronegativity | 5.50 |
Density
kg m -3 | 124.8 [b.p.]
0.1785 [273 K] |
| Molar Volume cm 3 | 32.07 [4K] |
Thermal Conductivity
W m -1 K -1 | 0.152 [300 K] |
| Melting Point K | 0.95 (under pressure) |
| Boiling Point K | 4.216 |
| Number of Isotopes | 5 |
| Inner + outer Shells | |
| Inner + outer Orbital(s) | |
| Filling Orbital | |
Ground State Electron
Configuration | 1s 2 = [He] |
|
Ground State Electron
Configuration with
free Orbitals (n= 0 )
|  |
|
Ground State Electron
Configuration with
compressed Orbitals (n= 0)
|  |
|
| Singularity | |
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| |
| Term Symbol | 1S 0 |
| Discovery | Observed by N. Lockyer and E. Frankland in the sun's spectrum during the eclipse of 1868. Isolated by Sir W. Ramsey (London, England) in 1895 and also by P.T. Cleve and N.A. Langlet (Uppsala, Sweden) |
| Name Derived From | Greek helios meaning 'sun'
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