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John Newland 1864
Only 63 elements known at the time, the remaining where yet
to be discovered.
He arranged the elements in order of their atomic masses.
He discovered that every eighth element in the pattern had
similar properties.
From this he created a periodic table of rows of 7.…read more

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Newland: Criticisms
Newlands ideas were criticised by scientists because:
When he reached the third row of eight, the transition metals
failed to fit the pattern. (Rows of 7 didn't work)
His groups did not contain elements with similar properties.
He mixed up metals and non metals.
Didn't consider the possibility of new elements and therefore,
did not leave gaps.…read more

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Dmitri Mendeleev 1869
Similar to Newland, he arranged known elements in order of
their atomic masses.
Difference between Newlands table is that he arranged the
elements in vertical groups of elements with similar
properties.
Major difference is that Mendeleev left gaps in his table for
any elements that may be undiscovered. These gaps allowed
scientist to predict the properties of elements yet to be
discovered.…read more

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Modern Day
Thanks to Mendeleev's decision to leave gaps in the periodic table in 1869,
scientist were able to fit newly discovered elements into the pattern
The periodic table is now based on electronic structures.
After the discovery of protons and neutrons, the periodic table is now
arranged in order of atomic or proton numbers.…read more

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