What is a substance that cannot be broken down to other substances by ordinary chemical means?

The correct answer is an element.

Explanation:

An element refers to a component whose atoms comprises a similar number of protons, or it can be said that the atoms of a specific element exhibit the same atomic number. Chemically, they are the simplest components, which cannot be further differentiated by any chemical means. The elements can get converted into other elements with the help of nuclear methods.

i think the answer is gold im not entirely sure