Antoine-Laurent Lavoisier was a French chemist (Born August 26, 1743 - died May 8, 1794) who's scientific contributions included establishing the law of the conservation of mass, determining that combustion and respiration are chemical reactions involving a chemical he named 'oxygen' and helping create chemical nomenclature (the system used to name elements), along with many others. Along with all the achievements listed above, he also gave new names to substances, most of which are still used today.
A German scientist called Johann Dobereiner put forward his law of triads in 1817. Each of Dobereiner's triads was a group of three elements. The appearance and reactions of the elements in a triad were similar to each other. At this time, scientists had begun to find out the relative atomic masses of the elements. Dobereiner discovered that the relative atomic mass of the middle element in each triad was close to the average of the relative atomic masses of the other two elements. This gave other scientists a clue that relative atomic masses were important when arranging the elements.
Newland's Law of Octaves states that 'if the chemical elements are arranged according to increasing atomic weight, those with similar physical and chemical properties occur after each interval of seven elements.'
Considered the 'father of the Periodic table', Dimitri Mendeleev distributed an Periodic table that allowed known elements to be gathered by their properties. When composing a science reading material for his understudies, He initially sorted out elements with comparative properties into families, then distinguished examples in the properties and weight of incandescent light and antacid metals. To widen this example, Mendeleev made cards for each of the 63 elements, taking note of their weights, and properties on each. When he organized the cards all together of climbing nuclear weight,, gathering elements of comparative properties together, the Periodic table was framed. Mendeleev's Periodic table made it conceivable to foresee properties of elements that had not yet been found. Mendeleev's work has been remembered throughout the years, with the 101st element being named Mendeleevium
Julius Lothar Meyer was a scientist who not only worked in the same field as Mendeleev, but also worked at the same time as Mendeleev (however neither scientist knew of each others work) and was taught by the same person as Mendeleev (Robert Bunsen). Meyer created many versions of his Periodic Table over around six years. He also created the 'Lothar Meyer Graph', showing the periodic trends of elements. Although he greatly contributed to Chemistry, his final paper was published just one year after Mendeleev's (in 1870).
Glenn Seaborg was a Nobel Science Prize winning scientist for his contribution to the periodic table. At the time of his works, the periodic table had developed far, far from Mendeleev's original periodic table- but still lacked many elements which are found on the table today. He discovered two elements, Californium and more notably Plutonium. Californium, the lesser known of the two, was first made in 1950 by Glenn Seaborg and his team consisting of Stanley Thompson, Kenneth Street Jr., Albert Ghiorso. It had been made by firing helium nuclei (alpha particles) at curium-242. It created the isotope now known as Californium-245 with a half-life of 44 minutes. Curium is very radioactive and it took years for the team to collect the few milligrams required. It only produced 5000 atoms of Californium, but the new element well and truly existed. Plutonium is a radioactive element which first found in 1940 by Glenn Seaborg and his team Arthur Wahl, Joseph Kennedy, and Edwin McMillan. They produced the plutonium by bombarding uranium-238 with deuterium nuclei. Originally from this experiment, they developed plutonium-238 with a half-life of only two days. This experiment created element 94.