History of the Periodic Table
- Two ways to categorise the elements
1) Physical and chemical properties 2) Relative atomic mass
- No such thing as atomic number until 20th century after protons and electrons were discovered.
- Known elements were arranged in the order of atomic mass, a periodc pattern was noticed in the properties of the elements.
Newlands' Law of Octaves
- Newland was the first person to arrange the elements usefully in 1864.
- Every 8th element had similar properties, so he listed the known elements in rows of 7
- These sets of eight were called Newlands' Octaves.
- His work was ignored because...
1) His groups contained elements thatt didn't have similar properties.
2) He mixed up metals and non-metals e.g oxygen and iron
3) He didn't leave gaps for elements yet to be discovered.
- In 1869, Dmitri arranged 50 known elements into his Table of Elements…