Merits and Demerits of Mendeleev’s Periodic Table

MERITS OF MENDELEEV’S PERIODIC TABLE:-

• Mendeléev left some gaps in his Periodic Table. Instead of looking upon these gaps as defects, Mendeléev boldly predicted the existence of some elements that had not been discovered at that time.
• Mendeléev named them by prefixing a Sanskrit numeral, Eka (one) to the name of preceding element in the same group. For instance, scandium, gallium and germanium, discovered later, have properties similar to Eka–boron, Eka–aluminium and Eka–silicon, respectively.
• When the noble gases were discovered, they could be placed in a new group without disturbing the existing order.

LIMITATIONS OF MENDELEEVS CLASSIFICATION:-

• No fixed position can be given to hydrogen in the Periodic table.
• Isotopes were discovered long after Mendeléev had proposed his periodic classification of elements. Position of isotopes could not be explained.
• Another problem was that the atomic masses do not increase in a regular manner in going from one element to the next. So it was not possible to predict how many elements could be discovered between two elements.