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... He described them as ‘primitive and simple’ substances, which is similar to the modern day definition:
“An element is a substance that cannot be split up into simpler substances by chemical means”
· It was an English chemist called Humphrey Davy who made some of the most important discoveries in the history of the elements. ...
History of the Periodic Table:
· By 1800, 50 elements (app. ... The work of four chemists led to the pattern of the periodic table- Johann Dobereiner, John Newlands, Dmitri Mendeleev and Henry Moseley. ... He stated this fact in his ‘Law of Octaves’:
“Newlands’ Octaves are groups of elements arranged in order of increasing atomic weight, in which the first and eighth element of each group have similar properties”
However, at present, we notice discrepancies in his table because Newlands did not realise that some elements had yet to be discovered meaning that his Law only works for the first sixteen elements. ... He found that if the elements were arranged in order of increasing atomic weight, then every eighth element had similar physical and chemical properties, summarised in the ‘Periodic Law’:
“When elements are arranged in order of increasing atomic weight (relative atomic mass), the properties of the elements vary periodically”
· Mendeleev’s Periodic Table of Elements differed to Newlands’ in two respects:
a) He left gaps in his table to make the elements fit into the proper column- the gaps represented elements that had yet to be discovered. ... In 1913, he found that frequencies varied with the quantity of the positive charge in the nucleus- he discovered a method of determining the number of protons in the nucleus of an atom, called the atomic number:
“The atomic number of an atom is the number of protons in the nucleus of that atom”
· Moseley was the man who made the final step from Mendeleev’s periodic table to the modern day periodic table.
Approximate Word count = 1405
Approximate Pages = 5.6
(250 words per page double spaced)
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