Which type of system must exist for chemical equilibrium

1. shared system
2. closed system
3. isolated system
4. open system

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.

Nonmetal are moldable and easily shaped