The first meaningful and remarkable contribution in the field of classification of elements was done by Russian Chemist by the name Dmitri I. Mendeleev in the year of 1869 and he proposed a law called Mendeleev periodic law which says that the physical & the chemical properties of the elements are a periodic function of their atomic masses.

In the table he made vertical columns called groups and vertical rows called as periods for the arranging the elements. There were nine groups & seven periods. He arranged only 60 elements in periodic table as only 60 elements were known at the time of Mendeleev.

The Modern Periodic law was proposed by an English physicist by the name Moseley, in 1913 which states that the physical & the chemical properties of the elements are the periodic function of their atomic number. He proved that atomic number and not the atomic mass is the most fundamental property of an element and is also play a key role in determining its physical and chemical properties. This law becomes the base or foundation of modern periodic law. In the modern periodic table there are 18 groups & 7 periods.