2
He
4.0026
Helium
Element 2 · 4.0026 u · s-block
noble gas
Second lightest element in the universe. An inert noble gas used in cryogenics, MRI machines, and party balloons.
Phase (STP)
Gas
Melting Point
—
Boiling Point
-268.93 °C
Density
0.0001785 g/cm³
Electronegativity
—
Atomic Radius
31 pm
Ionization Energy
2372 kJ/mol
Electron Affinity
0 kJ/mol
Discovered
1868 · Pierre Janssen
Electron Configuration
1s2
Electron Orbitals
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