2
4.0026 u
He
Helium
Noble Gas
Atomic Structure
Physical State
Group
18
Period
1
Block
s
Electron Configuration
1s²
Physical Properties
Atomic Mass:
4.0026 u
Electronegativity:
N/A
Atomic Radius:
140 pm
Ionization Energy:
24.587 eV
Density:
0.0001785 g/cm³
Melting Point:
0.95 K
Boiling Point:
4.22 K
Historical Information
Discovered By:
Pierre Janssen
Year Discovered:
1868