What did the chemist say when someone asked if he had any Sodium Hypobromate?

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.

In any atom of any element, you will find protons and neutrons in the nucleus of any atom 

Don’t know. don’t care.look it up on google