Here's why:

* Element: A pure substance made up of only one type of atom (like gold, oxygen, or carbon).

* Compound: A substance formed when two or more different elements are chemically combined in a fixed ratio (like water, which is H₂O, or salt, which is NaCl).

* Mixture: A combination of two or more substances that are not chemically bonded and can be separated by physical means (like sand and water).

Muriatic acid is actually the common name for hydrochloric acid (HCl). It is formed by the chemical combination of hydrogen (H) and chlorine (Cl) atoms.