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Joe Miles The Periodic Table of Elements
The Arrangement of the Periodic Table
In the early 1860's, John Newlands noticed that if you put the elements in the
order of their atomic mass, every eighth element had similar properties. He
called this his "Law of Octaves".
This was one of the first periodic tables and when it was released it contained
all of the elements. It was arranged by atomic mass.
However, there were disadvantages to this idea. The first row included metals
such as F, Cl, Br and I which have similar chemical properties, however it also
included elements with completely different chemical properties such as Co,
Ni, Pd, Pt and Ir. In addition, new elements were regularly being discovered,
and Newlands left no space in his table for these new elements.
Five years before the announcement of Dmitri Mendeleev's periodic table,
Lothar Meyer had produced a table of just 28 elements. These 28 elements
were mostly main group elements. He incorporated transition metals in another
table in 1868 which listed the elements in increasing weight order with
elements with the same valence in a given column. This was earlier than
Mendeleev's table (1869) but unfortunately Meyer's was not published until
In 1869, Dmitri Mendeleev published "Principles of Chemistry". This included
his version of the periodic table, in which he arranged the 63 known elements
based on atomic mass. The elements with similar chemical properties were in
the same groups. He predicted the existence and properties of new elements
and pointed out accepted atomic weights that were in error. Therefore, he
broke the strict rule of them being ordered exactly in atomic weight so that he
could leave room for other elements that had not yet been discovered.
Below is the version of the periodic table by Dmitri Mendeleev that has been