This German scientist put forward his law of triads. In each of the triads the element had similar appearances and chemical reactions. He discovered that the relative atomic mass of the middle element in each triad was roughly the average of the other 2 atomic masses. This helped other scientists figure out that atomic masses were important when arranging the elements.
This English chemist ordered all the elements in atomic weight and noticed that every 8 elements had similar chemical and physical properties. He called this model the ‘law of octaves’.
This Russian chemist created a periodic table which also had the elements in order of atomic weight but also had the elements with similar properties underneath each other. He also left gaps for other elements to be discovered.
This Scottish chemist invented a new section of the periodic table that obtained noble gases.
This English physicist discovered the atomic number for every element. When doing this he realised that by ordering the elements in atomic number rather than atomic weight the periodic table would fit together better.
This American chemist created a new section of the periodic table called ‘actinides’. He made this new section when he artificially produced heavy mass elements (neptunium).