Periodic Table
2
He
4.0026
Helium
Noble GasInert noble gas, second most abundant element in the universe.
Electronic Configuration
1s²or1s²
Electron shells
2e⁻n=1
Properties
Atomic number
2
Atomic mass
4.0026 u
Category
Noble Gas
Block / Group / Period
s · 18 · 1
Valence electrons
2
Oxidation states
0
Electronegativity
—
Atomic radius
31 pm
Ionization energy
2372 kJ/mol
Electron affinity
0 kJ/mol
Melting point
1 K / -272 °C
Boiling point
4 K / -269 °C
Density
0.00018 g/cm³
State at 25 °C
gas
Personal Notes
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