Question

the smallest thing that can be called an element is an _______
compound
sub particle
carbon
atom

Explanation:

An element is a pure substance made of only one kind of atom. Atoms are the smallest unit of an element that still has the properties of that element. Compounds are made of different elements combined chemically. Sub - particles like protons, neutrons, and electrons make up an atom but are not elements on their own. Carbon is an example of an element, but the smallest entity of an element is an atom.

Answer:

atom