(a) State Mendeleev’s periodic law.
(b) What chemical properties of elements were used by Mendeleev in creating his periodic table?
(c) State any three limitations of Mendeleev’s classification of elements.
(d) Besides gallium, which two other elements have since been discovered for which Mendeleev had left gaps in his periodic table ?
(e) Which group of elements was missing from Mendeleev’s original periodic table?


(a)  Mendeleev’s periodic law states that the properties of elements are a periodic function of their atomic masses.

(b) The elements having similar chemical properties form oxides and hydrides have similar formulas. Mendeleev used these properties for creating his periodic table.

(c) Limitations of Mendeleev’s classification of elements are given below::
  1. It failed to explain the position of isotopes.
  2. The wrong order of atomic masses of some elements could not be explained.
  3. A position for hydrogen could not be assigned in the periodic table.

(d) Silicon and Germanium two other elements have since been discovered for which Mendeleev had left gaps in his periodic table.


(e) Noble gases were missing from Mendeleev’s original periodic table. 

Updated on: 10-Oct-2022

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