What are the demerits of mendeleev periodic law ?
Answers
Answer:
Lightest elements were placed after heavier elements.
Position of hydrogen was not defined.
Explanation:
Demerits of mendeleev periodic table:
1.Atomic mass of elements Cobalt and nickel is same that is 59 therefore there was an ambiguity regarding the sequence of these elements in the mendeleev periodic table
2. isotopes were discovered long time after mendeleev developed the periodic table. isotopes have same chemical properties but different atomic masses, therefore isotopes could not be given a proper place in mendeleev periodic table
3.In periodic table elements are arranged in increasing order of atomic masses. the the rising atomic mass is not uniform. hence it was not possible to predict the number of elements that could be discovered between two heavy elements.
4. no fixed position was given to hydrogen in mendeleev periodic table because it resemble alkali metals as well as halogens