Question

why is an element considered a pure substance?

Explanation:

A pure substance has a uniform and definite composition. An element is made up of only one type of atom. Since all the atoms in an element are of the same kind, it has a consistent and unchanging composition throughout. This meets the criteria for a pure substance.

Answer:

An element is considered a pure substance because it is composed of only one type of atom, giving it a uniform and definite composition.