Latin name | Helium |
English name | Helium |
chemical symbol | He |
atomic number | 2 |
relative atomic mass | 4.002602 |
period | 18 |
group | VIII.A |
classification | noble gases |
discovery date | 1868 |
discoverer | Janssen, Ramsey Frankland, Lockyer |
melting point [°C] | -272,2 |
boiling point [°C] | -268,93 |
critical temperature [°C] | -267,96 |
critical pressure [MPa] | 0,227 |
density [g cm-3] | 0,0001787 |
electronegativity [Pauling] | 3,89 |
oxidation states | 0 |
electron configuration | 1s2 |
atomic radius [pm] | 31 |
covalent radius [pm] | 32 |
specific heat [J g-1K-1] | 5,193 |
heat of fusion [kJ mol-1] | - |
thermal conductivity [W m-1 K-1] | 0,1513 |
1. ionizing energy [kJmol-1] | 2372,323 |
2. ionizing energy [kJmol-1] | 5250,512 |
state at normal conditions | gas |
Helium is a colorless, light, monoatomic noble gas. Under normal conditions, does not create any helium stable compounds.