<text><span class="style10">lements and the Periodic Table (7 of 8)</span><span class="style7"></span><span class="style10">THE HISTORY OF THE PERIODIC TABLE</span><span class="style7">The discovery of the Periodic Table was made possible by an Italian chemist, Stanislao Cannizzaro (1826-1910), who in 1858 published a list of fixed atomic weights (now known as relative atomic masses) for the 60 elements that were then known. By arranging the elements in order of increasing atomic weight, a curious repetition of chemical properties at regular intervals was revealed. This was noticed in 1864 by the English chemist John Newlands (1838-98), but his 'law of octaves' brought him nothing but ridicule. It was left to the Russian chemist Dmitri Ivanovich Mendeleyev (1834-1907) to make essentially the same discovery five years later. What Mendeleyev did, however, was so much more impressive that he is rightly credited as the true discoverer of the Periodic Table.While working on his </span><span class="style26">Principles of Chemistry</span><span class="style7"> in 1869, Mendeleyev wrote the names and some of the main features of the elements on individual cards, to help establish a suitable order in which to discuss their chemistry. It was while arranging this pack of cards in different ways that he stumbled upon the pattern we now recognize as the Periodic Table. Mendeleyev laid out his cards in order of the atomic weights of the elements, placing together elements that formed similar oxides. By arranging similar elements in columns, he established the arrangement of the Table that has been followed ever since.Mendeleyev's genius lay in the fact that he recognized that there was an underlying order to the elements - he did not design the Periodic Table, he discovered it. If he was right, he knew that there should be places in his table for new elements. He was so confident in his discovery that he predicted the properties of these missing elements - and his predictions were subsequently shown to be accurate. In some cases, Mendeleyev also swapped the order of atomic weights, so that similar elements appeared in the same groups. This apparent anomaly was not explained until 1913, when the theory of isotopes was put forward.</span></text>
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<text>ΓÇó QUANTUM THEORY AND RELATIVITYΓÇó ATOMS AND SUBATOMIC PARTICLESΓÇó CHEMICAL BONDSΓÇó CHEMICAL REACTIONSΓÇó METALS</text>
