Potassium and calcium are rarely found as pure elements in nature. They are usually combined with other substances. Explain why is this so.

Potassium and calcium are rarely found as pure elements in nature but are usually combined with other substances because of their high reactivity.

Reactivity of elements refers to the ability of atoms of elements to gain or lose electrons in order to form bonds with other elements.

The most reactive elements are those of group 1, 2 and 7.

Because of their reactivity, they do not occur free in nature but in combined forma with other elements. Example is potassium.

They are very reactive as well and lose their two valence electrons easily to forms ions. Because of their reactivity, they do not occur free in nature but in combined forma with other elements. Example is calcium.

Therefore, potassium and calcium are rarely found as pure elements in nature but are usually combined with other substances because of their high reactivity.

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