Actually there are 3 inventors of the periodic table
1. Johann Dobereiner -he made an observation that bromine chemical and physical properties somewhere between those of chlorine and iodine and that bromine's atomic weight was almost midway between tose of chlorine and iodine. He
later found two more groups of similar elements; the first was calcium, strontium and barium; the second was sulfur, selenium and tellurium. He called these groups as TRIADS. also known as Law of Triads.
2. John Newlands - tried to arrange all the known elements in order of increasing atomic weight. He hit on the idea of arranging them in vertical columns. Since he noticed that the eight element had chemical and physical properties similar to the first, he let the eight elements start a new column. He called his arrangement as the Law of Octaves. But there were many places in his arrangement where dissimilar elements were next to each other.
3. Dmitri Mendeleev - arranged the elements so that their order depend on the similaritt of their chemical properties. Mendeleev established horizntal rows or periods. The hydrogen itsel made up the first period. The next two periods each contained seven elements. The period after that contained morethan seven elements.