They had no idea of atomic structure or of Protons and Electrons, so atomic number did not exist to them
They could only measure relative atomic mass therefore the known elements were arranged in order of atomic mass. When this was done a periodic pattern was noticed in the properties of the elements. This is where the name of the Periodic Table comes from.
Elements were catergorised into: their physical and chemical properties, their relative atomic mass
Newlands' Law of Octaves
Newlands in 1864 noticed that every eighth element had similar properties so he listed some of the…