Atomic Element Z = 2 • Noble Gas
Helium (He) — Atomic Data, Electron Shells & Reactions
Helium (symbol He, atomic number 2) has a standard atomic weight of 4.0026 u and ground-state configuration 1s2.
Atomic Number (Z)
2
IUPAC Symbol
He
Standard Atomic Weight
4.0026 g/mol
Period / Group / Block
1 / 18 / s-block
Condensed Electron Config
1s2
Full Subshell Config
1s2
Principal Shell Occupancy
[2]
Pauling Electronegativity
—
First Ionization Energy
2372 kJ/mol
Covalent Radius
28 pm
Melting Point
0.95 K (-272.20 °C)
Boiling Point
4.22 K (-268.93 °C)
Density
0.0001785 g/cm³
Oxidation States
0
He (Z=2) — Valence shell highlighted in vermilion