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Chemistry (Salters) Open-Book Paper 14 February 2004 History of Periodic Table German chemist Johann Dobereiner was the first to attempt to classify elements using their atomic weights (now known as relative atomic mass). He identified triads in the list of elements, for each triad the atomic weight of the middle element was approximately the average of the other two. In 1863, John Newlands noted that when the elements were written in order of increasing atomic weight, every eighth element had similar properties. So Newlands tried to produce a new periodic table based on his discovery but after about 20 elements his table became ragged; he had to put two elements in one space and some elements were in the wrong place because Newlands used inaccurately measured atomic weights. Still, Newlands was quite close to the right answer. Newlands' Octaves H Li Ga B C N O F Na Mg Al Si P S Cl K Ca Cr Ti Mn Fe Co,Ni Cu Zn Y In As Se Br Rb Sr Ce,La Zr Di,Mo Ro,Ru Pd Ag Cd U Sn Sb Te I Cs Ba,V Ta W Nb Au Pt,Ir Tl Pb Th Hg Bi Cs The Modern Periodic Table The...

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