The first classification was proposed by Döbereiner this chemist was able to find the relation between chemical proprieties and atomic mass he had the idea to gather elements in sets of three elements each element had similar chemical behavior and atomic mass, with a set of 20 group this was the first time any one could make a classification of the chemical elements known at that time
Chancourtois et Newlands
In 1862 Chancourtois et Newlands a french geologist and English scientist were able to notice a periodic trend in the characteristics of chemical elements they noticed that each time yu have eight elements in front of you will notice that the first one is similar to the eighth in a big way
Meyer
Around the year 1869 Meyer german chemist made more work on the periodic trend of the elements according to their atomic mass
Than the russian scientist Dmitri Mendeleïev around the year 1870, it was essentially an arrangement of 63 element known at that time according to Atomic mass and also according to the chemical proprieties, also the periodic table had some empty cases for further discoveries and new elements, by the year 1875 Gallium was discovered that’s Ga in the periodic table, Gallium had similar chemical behavior to the aluminium and we should mention that Mendeleïev mathematically predicted that such an element does exact with the exact characteristic.
In 1886, scientist discovered Germanium it results and can be found exclusively after melting zinc after two decades exactly in 1910 Protons were discovered and the number Z was introduced, this changed the whole classification principles and scientist started arranging elements according to two parameters M and Z after this further parameters were introduced like electron number.
The periodic table as we know it today is the result of many years of work of honorable scientist as mentioned above, the last version is the 2014 version with 118 elements.
