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Compare Potassium vs Francium

Comparing Potassium (K) and Francium (Fr). Atomic numbers 19 and 87 with atomic masses 39.098 u and 223 u, classified as alkali metal and alkali metal. 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
K
Potassium
#19
Fr
Francium
#87

Periodic properties of the elements

PotassiumFrancium
SymbolKFr
Atomic number1987
Group11
Period47
Blockss
Element categoryAlkali MetalAlkali Metal

Physical properties

PotassiumFrancium
Phase at STPSolidSolid
Density0.862 g/cm31.87 g/cm3
Atomic weight39.0983 u223 u
Melting point336.7 K
63.55 °C
146.39 °F		300 K
26.85 °C
80.33 °F
Boiling point1032 K
758.85 °C
1397.93 °F		950 K
676.85 °C
1250.33 °F

Atomic properties

PotassiumFrancium
Electronegativity (Pauling Scale)0.820.79
Electron affinity48.383 kJ/mol46.89 kJ/mol
Oxidation states−1, +1
(a strongly basic oxide)		+1
(a strongly basic oxide)
Ionization energies
  1. 418.8 kJ/mol
  2. 3052 kJ/mol
  3. 4420 kJ/mol
  4. 5877 kJ/mol
  5. 7975 kJ/mol
  6. 9590 kJ/mol
  7. 11343 kJ/mol
  8. 14944 kJ/mol
  9. 16963.7 kJ/mol
  10. 48610 kJ/mol
  11. 54490 kJ/mol
  12. 60730 kJ/mol
  13. 68950 kJ/mol
  14. 75900 kJ/mol
  15. 83080 kJ/mol
  16. 93400 kJ/mol
  17. 99710 kJ/mol
  18. 444880 kJ/mol
  19. 476063 kJ/mol
  1. 380 kJ/mol

Electron configuration

PotassiumFrancium
Shorthand configuration[Ar] 4s1 [Rn] 7s1
Full configuration1s2 2s2 2p6 3s2 3p6 4s1 1s2 2s2 2p6 3s2 3p6 3d10 4s24p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 7s1
Electrons per shell2, 8, 8, 12, 8, 18, 32, 18, 8, 1

History

PotassiumFrancium
DiscoveryHumphry Davy (1807)Marguerite Perey (1939)
First isolationHumphry Davy (1807)Marguerite Perey (1939)
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