2He
Helium
Noble GasHelium (He) is element 2, a noble gas, in period 2 and group 18 of the periodic table. Its standard atomic weight is 4.003, it melts at -272.2 °C and boils at -268.93 °C. Discovered by Pierre Janssen, 1868.
Atomic Number2
SymbolHe
NameHelium
Atomic Weight4.003 u
CategoryNoble Gas
Period2
Group18
Melting Point-272.2 °C
Boiling Point-268.93 °C
Density0.000164 g/cm³
Electron Config1s2
Discovered ByPierre Janssen, 1868