Answer: one kind of atom
Step-by-step explanation:
Element is a pure substance which is composed of similar atoms.It can not be decomposed into simpler constituents using chemical reactions.Example: Aluminium

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: water

Thus as aluminium is made up of one kind of atom , it is considered as an element.