Chemical reactions and the periodic table

As the years progressed, the methods of analysis become more accurate and precise. Scientists were able to detect very small quantities of materials and the structures were worked out. In modem times chemical analysis is done by very accurate and sophisticated techniques. These methods will be discussed in Chapter 11. 

Whenever elements and compounds react together to form a stable compound, the atoms always try to rearrange the outer electrons to achieve a complete outer electron shell of two or eight. These complete shells were found to be the structures of the elements in group 8 of the periodic table. 

The scientists of the nineteenth century discovered new materials that they found to be made up of combinations of simple elements. They began to compare the masses of these elements and discovered that this property was a fundamental characteristic of the element - its atomic mass. 

In 1896 a Russian scientist called Mendeleev found that these numerical values could be put into an ordered pattern which he called the periodic table, which was completed later when more elements were discovered. In about 1932 scientists found that the fundamental property that sequenced the elements in their periodic table order was not their mass but the number of protons in their nucleus. This property is called the atomic number, and every element has its own unique atomic number. 

In the periodic table according to atomic number all the elements are put in order, each element differing by one unit from its neighbour. It is that simple (See Appendix 2 for the periodic table.) 

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