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2 - Helium noble gas

Discovered by Pierre Janssen in 1868


Helium is a chemical element with symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table. Its boiling and melting points are the lowest among all the elements.

Shell Electrons Orbitals
1 2 2 in 1s
HeliumHe Electron 1 Electron 2
4  u Atomic Mass
0.49  Å Atomic Radius
4.22  K Boiling Point
0.28  Å Covalent Radius
0.000179  g/cm³ Density
−48 Electron Affinity
24.6  eV First Ionization Energy
1 Number of Shells
2 Atomic Number
2 Electron Shell Occupations