2 - Helium noble gas

Discovered by Pierre Janssen in 1868

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Helium

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.

Periodic table

 Shell Electrons Orbitals
122 in 1s

Electron shells

colorless gas, exhibiting a red-orange glow when placed in a high-voltage electric field Appearance
4  u Atomic Mass
4.22  K Boiling Point
18 Group
0.28  Å Covalent Radius
0.000179  g/cm³ Density
−48  kJ/mol Electron Affinity
1s2 Electron Configuration
1s2 Electron Configuration (semantic)
2 Electrons
24.6  eV First Ionization Energy
2372.3, 5250.5  kJ/mol Ionization Energies
1 Mendeleev Number
1 Number of Shells
2 Neutrons
2 Atomic Number
5 Number of Isotopes
1 Period
Gas Phase
2 Protons
2 Electron Shell Occupations
5.19  J/(g K) Specific Heat