Why are sodium and potassium common in Earth’s crust?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

A color-coded periodic table of the elements displays each element's symbol and atomic number, with categories such as alkali metals, noble gases, halogens, transition metals, and actinoid elements distinguished by different background colors. — alkali metal Modern version of the periodic table of the elements (printable).

Sodium and potassium are among the most abundant elements in Earth’s crust, ranking as the sixth and seventh most common elements, respectively. They are widely distributed because they are key components of various igneous rocks, shale, and sediment, where they exist within complex, water-insoluble minerals such as feldspar and muscovite.12

While these elements are highly reactive and readily form soluble salts—such as halite (sodium chloride) and sylvite (potassium chloride)—found in ancient lake beds and seabeds, their presence in the crust is primarily maintained by their integration into stable, insoluble mineral structures. These minerals protect the elements from being easily leached away, ensuring their continued prevalence throughout the Earth's crustal composition.12