A substance made up of only atoms of one type is called

chemical element

Explanation: A chemical element is a substance that contains only one type of atom, which is the smallest particle of an element.

 What is an example of a substance that is made of only one type of atom?

A substance of only one type of atom would be a pure substance from any of the elements in the period table. A common example could be nitrogen, N2, which is easily isolated, or gold, Au, which tends not to form compounds with other elements.

If we consider any real volume of a real material, there will be impurities; small amounts of other elements. On earth, we have been able to refine silicon, Si, to a highly pure state. This may be the best example of a substance of only one type of atom. There may be other better answers such as some parts of a star contain only hydrogen, H, or helium, He.

Explanation:

The answer may depend on how tolerant you are to impurity, and whether you count different isotopes as same or different type of atom.

In principle, you might simply walk through the periodic table and for each element check if it exists in a pure form …