Answer: element
Explanation:
Element is a pure substance which is composed of similar or one type of atoms.It can not be decomposed into simpler constituents using chemical reactions.Example: Gold \(Au\)
Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: carbon dioxide \(CO_2\)
Mixture is a substance which has two or more components which do not combine chemically and do not have any fixed ratio in which they are present. Example: air
