what are substances that cannot be broken down into simpler substances?\no elements\no protons\no…

what are substances that cannot be broken down into simpler substances?\no elements\no protons\no molecules\no compounds
Answer
Brief Explanations:
Elements are substances that cannot be broken down into simpler substances by chemical means. Protons are sub - atomic particles, molecules are made up of atoms, and compounds are made up of two or more different elements chemically combined.
Answer:
elements