Respuesta :
The only property which was used previously for the arrangement of elements was atomic mass.
The periodic arrangement as started by Dobereneir as triads used atomic mass
the octave arrangement by Newland was also based on atomic mass
The periodic arrangement which was majorly accepted by the chemical world was given by Mendleev. Who arranged by then elements based on their atomic masses. He infact left spaces for the unknown or not discovered elements based on atomic mass.
However, this atomic mass is no longer used for periodic arrangement of elements. Now the modern periodic table or law is based on atomic number.
