Compare and contrast the arrangement of elements in Mendeléev’s Periodic Table and the Modern Periodic Table.

Explanation

(i) In Mendeleev.s periodic table the elements are arranged in the increasing order of atomic mass. On the other hand, in the Modern Periodic Table the elements are arranged in the increasing order of atomic numbers which is more fundamental property than the atomic mass.
(ii) In the Mendeleev.s periodic table, the position of the elements was in accordance with atomic mass. In the Modern Periodic Table the position of the elements is governed by electronic configurations, which determine their properties.
(iii) In Mendeleev.s periodic table, the position of isotopes was not justified. In Modern Periodic Table, the classifications is based on the atomic number and not atomic mass and hence the position of isotopes is fully justified.
(iv) Mendeleev.s periodic table had some anomalies on the basis of atomic mass. In Modern Periodic Table, there are no misfits in terms of atomic number. For example, in Mendeleev.s periodic table, potassium was having position lower than argon. But in Modern Periodic Table, this has been solved. Argon precedes potassium because argon has atomic number 18 and potassium has 19.
(v) The Mendeleev.s periodic table does not explain satisfactorily as to why the properties of the elements are repeated at regular intervals of 2, 8, 18 and 32. The Modern Periodic Table explains this logically.
(vi) There is no clear cut separation of different types of elements in the Mendeleev.s periodic table. In modern periodic table there is clear cut separation of different types of elements such as representative elements, noble gases, transition elements.
(vii) Mendeleev.s periodic table is not easy to remember. Modern Periodic Table is easy to remember.