Chemistry unit 3 GCSE

Unit 3 revision

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History of the periodic table

  • Early 1800's - atomic mass
  • Newlands law of octaves 
  • Demitri Mendeleev 
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EARLY 1800'S 

  • 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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