One of the following properties was originally used to arrange elements on the periodic table, but is no longer used to organize the modem version. Which property fits this description?
atomic number
O atomic mass
chemical properties

atomic mass

Explanation:

A British chemist named John Newlands  organized the elements known at that time into a system of  periodicity based on an order of increasing atomic masses.

In his table, it was found that every eight elements had similar properties. He called this observation the law of octaves.

Currently, the periodicity of elements is based on increasing atomic numbers and this is generally called the modern periodic law.