Potassium is a reactive metal whose compounds are important in fertilizers and whose ions occur throughout living cells. Plants obtain potassium from soil, so removing crops also removes this nutrient. Natural potassium includes potassium-40, linking ordinary matter to radioactive processes.
FROM ELEMENT TO APPLICATION
AN ELEMENT IN CONTEXT
Why does a potassium fertilizer’s compound form matter?
Potassium salts in fertilizers
FOLLOW THIS RELATIONSHIP
Start with a potassium salt
Fertilizer products supply potassium in compounds, linking the nutrient to ions and counterions rather than to a reactive sample of elemental metal.
Explore the model (optional)
KFORM → INTERACTION → CONSEQUENCE
Follow the explanation in either direction. These are authored steps, not a physical clock.
Potassium compounds had long supported crafts and industry: potash entered soapmaking, while other salts served dyeing and related trades. The metal remained unknown because it reacts readily and occurs naturally in compounds. In 1807 Davy applied electricity to potash and obtained potassium. This work helped show that substances previously grouped as earthy or alkaline materials could conceal distinct, highly reactive metallic elements.
Before 1807
Potassium compounds used
Potash salts supported established crafts.
1807
Metal isolated
Davy obtained potassium through electrochemical investigation of potash.
Potassium occurs in dissolved salts and including sylvite, carnallite, and feldspar-bearing materials. Some salt deposits formed as ancient waters evaporated. These sources contain potassium chemically combined, providing a contrast with the reactive free metal and linking potassium's industrial supply to both mineral deposits and aqueous geochemistry.
Potassium is a soft, silvery alkali metal that readily tarnishes and reacts strongly with water. Its compounds span materials with very different behavior, including common mineral salts. The characteristic color produced by potassium-containing samples in a flame reflects atomic excitation, rather than proving that the original sample was pure metal.
Each section links its supporting references. Descriptions and diagrams were authored for this atlas. Source checks completed. Source checks dated 2026-09-06.
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Family labels and the group-3 layout are teaching conventions. A table position does not establish an unknown bulk property. Electronic configurations refer to neutral atoms; ions and material environments require their own account.
Read each reference property together with its units, conditions and the reference information below.
Not yet recorded: electron affinity, second ionization energy, ground-state term symbol, van der waals radius, thermal conductivity, specific heat capacity, electrical resistivity, crystal structure, lattice parameter a, space group, abundance in seawater, abundance in the universe, annual production, supply-risk listing, hazard classification, biological role, cas registry number, pubchem cid, wikidata item. These families are declared and awaiting an ingestion run against the source each names; they are listed here rather than shown as empty rows.
Physical
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Phase at 20 °C
solid
293.15 K, 101.325 kPa
Melting point in K
336.53 K
at standard pressure unless noted
Boiling point in K
1032 K
101.325 kPa
Density in g/cm³
0.862 g/cm³
solids and liquids at 293 K; gases at 273 K and 101.325 kPa
Atomic and electronic
Intended reference: Pauling electronegativity scale · Widely tabulated; original in The Nature of the Chemical Bond
Electronegativity in Pauling
0.82 Pauling
Pauling scale
First ionization energy in kJ/mol
418.8 kJ/mol
gas-phase neutral atom, ground state
Covalent radius in pm
203 pm
single-bond covalent radius
Common oxidation states
+1
states met in ordinary compounds; not exhaustive
Occurrence and identity
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Abundance in the crust in mg/kg
20900 mg/kg
upper continental crust, mass fraction
Has stable isotopes
Yesderived
Discovery year in CE
1807 CEderived
WHERE IT SITS AMONG ITS NEIGHBORS
Electronegativity across period 4
K 0.82 Pauling · Potassium
Electronegativity across period 4. Exact values.
K
0.82
Ca
1
Sc
1.36
Ti
1.54
V
1.63
Cr
1.66
Mn
1.55
Fe
1.83
Co
1.88
Ni
1.91
Cu
1.9
Zn
1.65
Ga
1.81
Ge
2.01
As
2.18
Se
2.55
Br
2.96
Kr
3
Electronegativity down group 1
K 0.82 Pauling · Potassium
Electronegativity down group 1. Exact values.
H
2.2
Li
0.98
Na
0.93
K
0.82
Rb
0.82
Cs
0.79
The trend uses the same reference-property values as the periodic table. Elements with no recorded value are left out of the line rather than drawn at zero.
