Question

Merits and demerits of Maldeleev's periodic table

Answer 1

Answer:

He was unable to locate hydrogen in the periodic table. Increase in atomic mass was not regular while moving from one element to another. Hence, the number of elements yet to be discovered was not predictable. Later on, isotopes of elements were found which violated Mendeleev's periodic law.

Answer 2

Explanation:

merits

1. Mendeleev was the first scientist make periodic table

2. Mendeelev kept vacant places for some elements till not discovered

3. he place the noble gases properly

demerits

1. the elements Cobalt and nickel have the same whole number atomic masses as remit there was an ambiguity regarding their sequence in Mendeleev periodic table

2. isotopes where discovered long time after Mendeleev put forth the periodic table a challenge was posed in placing isotopes in Mendeleev periodic table as isotopes have the same chemical properties but different atomic masses

3. the rise in atomic masses does not appear to be uniform when elements are arranged in increasing order of atomic masses it was not possible therefore predict how many elements could be discovered between two heavier elements

4. position of hydrogen: hydrogen show similarity with halogens for example the molecular formula of hydrogen is used while other molecular formula of fluorine and chlorine are F2 and cl2 respectively in the same way there is a similarity in the chemical properties of hydrogen and alkali metals there is a similarity in the molecular formula of the compounds of hydrogen alkali metals

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