2 - Helium noble gas

Discovered by Pierre Janssen in 1868

  • Atomic Radius (Å)
  • Cividis
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.

H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og
57-71 La-Lu Lanthanides
89-103 Ac-Lr Actinides
 Shell Electrons Orbitals
122 in 1s
HeliumHeElectron 1Electron 2
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