History of the periodic table
- Early 1800's - atomic mass
- Newlands law of octaves
- Demitri Mendeleev
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- There were two obvious ways of categorising elements: 1) Their physical and chemical properties 2) Their relative atomic mass
- They had no idea of atomic structure, protons or electrons so there was no such thing as an atomic number.
- The only thing they could measure was the relative atomic mass and so known elements were arraned in order of the relative atomic mass. When this was done, a periodic pattern was noticed in the properties of the elements.
NEWLANDS LAW OF OCTAVES
- He noticed that every eighth element had similar properties, so listed the known elements in rows of 7.
- The sets of eight were known as Newlands' octaves.
- It was because he left no gaps that his work was ignored.
- His work was criticised because: 1) his groups
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