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Compare Helium vs Krypton

Comparing Helium (He) and Krypton (Kr). Atomic numbers 2 and 36 with atomic masses 4.003 u and 83.798 u, classified as noble gas and noble gas. Below: a side-by-side comparison of their physical, atomic, electron-configuration and historical properties, including density, melting and boiling points, ionization energies, oxidation states and discovery history.

vs
He
Helium
#2
Kr
Krypton
#36

Periodic properties of the elements

HeliumKrypton
SymbolHeKr
Atomic number236
Group1818
Period14
Blocksp
Element categoryNoble GasNoble Gas

Physical properties

HeliumKrypton
Phase at STPGasGas
Density0.1786 g/cm33.749 g/cm3
Atomic weight4.0026 u83.7982 u
Melting point0.95 K
-272.2 °C
-457.96 °F		115.78 K
-157.37 °C
-251.266 °F
Boiling point4.222 K
-268.928 °C
-452.0704 °F		119.93 K
-153.22 °C
-243.796 °F

Atomic properties

HeliumKrypton
Electronegativity (Pauling Scale)03
Electron affinity-48 kJ/mol-96 kJ/mol
Oxidation states00, +1, +2
(rarely more than 0; oxide is unknown)
Ionization energies
  1. 2372.3 kJ/mol
  2. 5250.5 kJ/mol
  1. 1350.8 kJ/mol
  2. 2350.4 kJ/mol
  3. 3565 kJ/mol
  4. 5070 kJ/mol
  5. 6240 kJ/mol
  6. 7570 kJ/mol
  7. 10710 kJ/mol
  8. 12138 kJ/mol
  9. 22274 kJ/mol
  10. 25880 kJ/mol
  11. 29700 kJ/mol
  12. 33800 kJ/mol
  13. 37700 kJ/mol
  14. 43100 kJ/mol
  15. 47500 kJ/mol
  16. 52200 kJ/mol
  17. 57100 kJ/mol
  18. 61800 kJ/mol
  19. 75800 kJ/mol
  20. 80400 kJ/mol
  21. 85300 kJ/mol
  22. 90400 kJ/mol
  23. 96300 kJ/mol
  24. 101400 kJ/mol
  25. 111100 kJ/mol
  26. 116290 kJ/mol
  27. 282500 kJ/mol
  28. 296200 kJ/mol
  29. 311400 kJ/mol
  30. 326200 kJ/mol

Electron configuration

HeliumKrypton
Shorthand configuration1s2 [Ar] 3d10 4s2 4p6
Full configuration1s2 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6
Electrons per shell22, 8, 18, 8

History

HeliumKrypton
DiscoveryPierre Janssen, Norman Lockyer (1868)William Ramsay, Morris Travers (1898)
First isolationWilliam Ramsay, Per Teodor Cleve, Abraham Langlet (1895)William Ramsay, Morris Travers (1898)
Named byEdward Frankland, Norman Lockyer (1868)
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