Atoms cannot be apart what fills in the blank?

Atoms cannot be Split apart but if they are it can actually cause an explosion as goes the saying "atomic bomb" or atomic energy

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.

Answers are 1,2,4 its correct on edgenuity.