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A History of the Periodic Table.

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Introduction

A HISTORY OF THE PERIODIC TABLE Introduction D�bereiners Triads In the early 1800s Dobereiner noted that many of the known elements could be arranged in triads - a group of 3 chemically similar elements. Two of these triads are Chlorine, Bromine, Iodine and Lithium, Sodium Potassium. D�bereiner's Triads Ca 40.1 Sr 87.6 Ba 137.3 S 32.1 Se 79.0 Te 127.6 Cl 35.5 Br 79.9 I 126.9 He showed that when the three elements in each triad were arranged in order of Relative Atomic Mass, the middle element had properties intermediate to those of the other two elements. Also the Relative Atomic Mass of the middle element was close to the mean Relative atomic Masses of the other two elements. ...read more.

Middle

Newlands' Octaves H Li Ga B C N O F Na Mg Al Si P S Cl K Ca Cr Ti Mn Fe Co,Ni Cu Zn Y In As Se Br Rb Sr Ce,La Zr Di,Mo Ro,Ru Pd Ag Cd U Sn Sb Te I Cs Ba,V Ta W Nb Au Pt,Ir Tl Pb Th Hg Bi Cs Newlands Octaves: The eighth element is a kind of repetition of the first like the eighth note of an octave in music. His work wasn't very well received by the scientific community because there weren't any empty spaces his table which assumed that all the elements had been discovered even though 4 elements had been discovered a few years before his work was published so the discovery of a new element could throw the idea out of the window. ...read more.

Conclusion

The peaks had alkali metals: sodium, potassium, rubidium, and caesium. Each fall and rise to a peak, corresponded to a period like the waves. In each period a number of physical properties other than atomic volume also fell and rose, such as valence and melting point. Figure below shows the curve obtained by Lothar Meyer when he plotted the atomic masses and the respective atomic volumes. Each peak started with a new period. Note the graph shows the inert gases which were discovered later in 1894 by William Ramsey. These elements represented a new group. Dimitri Mendeleev The most famous work that was done in developing the periodic table was done by a Russian chemist, Dmitri Mendeleev. Mendeleev developed his periodic table in 1869. It was a table, not a graph. http://home.att.net/~cat6a/class_elem-III.htm http://dl.clackamas.cc.or.us/ch104-07/mendeleev_3.htm Mohammed Seedat 1 ...read more.

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