Definition:Potassium

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Chemical Element

Potassium is the chemical element that has $19$ protons in the nuclei of its atoms

Its chemical symbol is $\text K$.

Isotopes

K-$40$

Potassium-$40$ is the isotope of potassium which has $21$ neutrons in addition to its $19$ protons.

K-$40$ is radioactive, with a half-life of approximately $1.251 \times 10^9$ years.

Linguistic Note

The word potassium derives from the word potash, from which potassium was first extracted.

Potash is a general name for the salts of potassium, manufactured in pre-industrial times from the ash of plants, processed in a pot.

Its symbol $\text K$ derives from the neo-Latin kalium, itself deriving from the Arabic word القَلْيَه‎ (al-qalyah) meaning plant ashes.