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Need for Periodic Classification of Elements
Chemists discovered that all the substances are made up of atoms or elements. Slowly they discovered many elements. In 1789, Antoine Lavoisier published a list of 33 elements. With the discovery of many elements chemists felt the need of classification of elements for their easy understanding and comparison. So, Antoine Lavoisier attempted to group all 33 elements into gases, metals, nonmetals and earth metals. Slowly by 1865, 63 elements were discovered. By now, chemists felt the need of periodic classification of elements as now it was very difficult to study the properties of these chemical elements individually. Scientists were trying to classify elements in a periodic manner of the basis of their various properties.
In the year 1869, Dmitri Mendeleev arranged all 63 elements in rows or columns in order of their atomic weight. He left the space for corresponding elements in his periodic table which were not even discovered then. Although he was able to predict the properties of those elements through his periodic classification of elements.
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Mendeleev’s Periodic Table from his book-‘An attempt towards a chemical conception of the Ether’
By 1911, scientists discovered atomic structure and atomic nucleus. Now they know the terms like isotope, proton etc. Mendeleev’s periodic table was not able to describe all this and was not able to assign position to isotopes and a perfect position to hydrogen according to its properties. So, in 1913 Mendeleev’s periodic table was perfected by Henry Moseley. He arranged all the elements in order of their increasing atomic numbers. This improved all the flaws of the Mendeleev Periodic Table. Such a position of hydrogen was fixed as its atomic number 1, there was no need for a separate position for isotopes as the arrangement was according to the atomic number of elements.
Presently, 118 chemical elements are known and are arranged in the Modern Periodic table. Out of 118 elements 98 elements occur naturally while 20 elements are man made in laboratories.
Significance of the Periodic Classification of Elements
Periodic table is very important as they classify elements according to their properties and provide us a great deal of information about elements and how they relate to one another. The organized classification of chemical elements in the periodic table has following advantages:
It enables chemists to easily understand properties of elements.
It comes very handy while performing experiments.
It enables chemists to compare the properties of elements.
It gives systematic and orderly information about elements and their compounds as well.
It enables chemists to predict the properties of even those elements which have not yet been discovered.
It provides information which can be used to easily balance the chemical equations.
It gives a proper explanation of the difference and similarity between properties of elements in groups and rows.
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