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Different scientists put forward different theories and models to explain how exactly elements could be classified based on certain similar chemical and physical properties.The need for the classification of elements to make their study easier was always challenging to us Dobereiner triads, Newlands law of octaves, Mendeleev's Periodic table, and the Modern periodic table given by Moseley remain the most common ones. The periodic table has gone through many changes sinceDmitri Mendeleev drew up its original design in 1869, yet both the first table and the modern periodic table are important for the same reason The periodic table organizes elements according to similar properties so you can tell the characteristics of an element just by looking at its location on the table.

In the modern periodic table, the elements are arranged based on the increasing atomic numbers and 118 elements are known to be added to this date.

The elements when arranged in increasing atomic numbers, repeat after a regular interval, and this property is known as periodicity and the elements are periodic functions of their atomic number.

The elements which are present in the same period have the same number of valence shells and those which are present in the same group have the same valence electronic configuration i.e. the number of electrons entering in the outermost orbit also known as the valence shell is the same in the same group. Since the number of valence electrons is also the same, so their chemical properties are similar too. Hence, the table is said to be periodic.