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Potassium (K)

Potassium is a chemical element of the periodic table with chemical symbol K and atomic number 19 with an atomic weight of 39.0983 u and is classed as alkali metal and is part of group 1 (alkali metal). Potassium is solid at room temperature.

Potassium in the periodic table

Atomic number19
Group1 (Alkali metal)
ClassificationAlkali Metal
AppearanceSilvery gray
Color Silver
Number of protons19 p+
Number of neutrons20 n0
Number of electrons19 e-
From Wikipedia, the free encyclopediaPotassium is a chemical element with symbol K (derived from Neo-Latin, kalium) and atomic number 19. It was first isolated from potash, the ashes of plants, from which its name is derived. In the Periodic table, potassium is one of seven elements in column (group) 1 (alkali metals):they all have a single valence electron in their outer electron shell, which they readily give up to create an atom with a positive charge - a cation, and combine with anions to form salts.

Physical properties

Phase at STPSolid
Density0.862 g/cm3
Atomic weight39.0983 u

Thermal properties

Melting point336.7 K
63.55 °C
146.39 °F
Boiling point1032 K
758.85 °C
1397.93 °F
Heat of vaporization76.9 kJ/mol

Atomic properties

Electronegativity (Pauling Scale)0.82
Electron affinity48.383 kJ/mol
Oxidation states−1, +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

Electron configuration for potassium

Electron configuration
Shorthand configuration
[Ar] 4s1
Electron configuration
Full configuration
1s2 2s2 2p6 3s2 3p6 4s1
Electron configuration chart
Electrons per shell2, 8, 8, 1
Valence electrons 1
Valency electrons 1
Bohr model
PotassiumElectron shell for Potassium, created by Injosoft ABK
Figure: Shell diagram of Potassium (K) atom.
Orbital Diagram

The history of Potassium

Discovery and first isolationHumphry Davy (1807)
Discovery of potassium
The English name for the element potassium comes from the word potash, which refers to an early method of extracting various potassium salts: placing in a pot the ash of burnt wood or tree leaves, adding water, heating, and evaporating the solution. When Humphry Davy first isolated the pure element using electrolysis in 1807, he named it potassium, which he derived from the word potash. The symbol K stems from kali, itself from the root word alkali, which in turn comes from Arabic: القَلْيَه al-qalyah 'plant ashes'. In 1797, the German chemist Martin Klaproth discovered "potash" in the minerals leucite and lepidolite, and realized that "potash" was not a product of plant growth but actually contained a new element, which he proposed calling kali. In 1807, Humphry Davy produced the element via electrolysis: in 1809, Ludwig Wilhelm Gilbert proposed the name Kalium for Davy's "potassium". In 1814, the Swedish chemist Berzelius advocated the name kalium for potassium, with the chemical symbol K.


List of unique identifiers for Potassium in various chemical registry databases
CAS Number7440-09-7
ChemSpider ID4575326
EC number231-119-8
PubChem CID Number5462222