Chemistry unit 3 GCSE

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

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