What is a key property of an element?

A key property of an element is that it cannot be broken down into simpler substances. This fundamental characteristic defines what an element is in the context of chemistry and the periodic table. Elements consist of atoms, and each type of atom corresponds to a different element. Since elements are the basic building blocks of matter, they maintain their unique properties and identities without being reducible to simpler forms.

The other options do not accurately represent the defining characteristics of elements. For instance, while some elements exist as ions, not all do, and this property does not apply universally. Elements also consist solely of one type of atom; therefore, they cannot contain multiple types of atoms, which would instead describe a compound. Lastly, elements can exist in different states of matter—solid, liquid, or gas—depending on the conditions, so saying they are always found in a fixed state is not accurate.