Question: Who Invented the Periodic Table?
Do you know who described the first periodic table of the elements that ordered the elements by increasing atomic weight and according to trends in their properties? I'll give you a hint. It was not Dmitri Mendeleev. The actual inventor of the periodic table is someone rarely mentioned in chemistry history books.
Answer: If you answered "Dmitri Mendeleev" then you might be incorrect. Dmitri Mendeleev presented his periodic table of the elements based on increasing atomic weight on March 6, 1869, in a presentation to the Russian Chemical Society. While Mendeleev's table was the first to gain some acceptance in the scientific community, it was not the first table of its kind.
John Newlands had published his Law of Octaves in 1865. The Law of Octaves had two elements in one box and did not allow space for undiscovered elements, so it was criticized and did not gain recognition.
A year earlier (1864) Lothar Meyer published a periodic table which described the placement of 28 elements. Meyer's periodic table ordered the elements into groups arranged in order of their atomic weights. His periodic table arranged the elements into 6 families according to their valence, which was the first attempt to classify the elements according to this property.
While many people are aware of Meyer's contribution to the understanding of element periodicity and the development of the periodic table, many have not heard of Alexandre-Emile Béguyer de Chancourtois. de Chancourtois was the first scientist to arrange the chemical elements in order of their atomic weights. In 1862 de Chancourtois presented a paper describing his arrangement of the elements to the French Academy of Sciences. The paper was published in the Academy's journal, Comptes Rendus, but without the actual table. The periodic table did appear in another publication, but it was not as widely read as the Academy's journal. de Chancourtois was a geologist and his paper primarily dealt with geological concepts so his periodic table did not gain the attention of the chemists of the day.
The modern periodic table orders the elements according to increasing atomic number rather than increasing atomic weight, but the earlier tables were true periodic tables since they grouped the elements according to periodicity of their chemical and physical properties. Protons, which define elements today, were unknown at the time.