What indicates that a chemical reaction has taken place explain why the indicator would be a sign of chemical reaction is not a sign of physical change

The answer is c) pyrite

High-energy and unstable.

Hello thereone of the following properties was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version. which property fits this description? answer: atomic mass  was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.