Question

What are the defects of Mendeleev's periodic table?

Answer 1

Mendeleev's periodic table:

• According to Mendeleev's periodic table, the elements were arranged in an order of increasing atomic mass.

Demerits of Mendeleev's periodic table:

• Certainly, no fixed position can be given to hydrogen in the Periodic table.
• There are three elements in the fourth, fifth, and sixth periods, the reason for which was not given.
• Isotopes were discovered long after Mendeléev had proposed his periodic classification of elements.
• The periodic table cannot accommodate the presently known 118 elements.
• "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 — especially when we consider the heavier elements"
• The elements present in Lanthanides and actinides that were discovered later, can not be placed in his periodic table.
• The periodic table contains elements of dissimilar properties together and separates elements of the same properties. Such as barium and lead are, separated into second and fourth groups.