Question

write the abnormalies of Mendeleev's Periodic table?​

Answer 1

Answer:

Some elements with similar properties were placed in different groups and those with dissimilar properties were placed in same group. Some elements with similar properties were placed in different groups and those with dissimilar properties were placed in same group.

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Answer 2

Explanation:

1. The whole number atomic mass of the elements cobalt (Co) and nickel (Ni) is the same.

Therefore there was an ambiguity regarding their sequence in Mendeleev’s periodic

table.

2. Isotopes were discovered long time after Mendeleev put forth the periodic table. As

isotopes have the same chemical properties but different atomic masses, a challenge

was posed in placing them in Mendeleev’s periodic table.

3. When elements are arranged in an increasing order of atomic masses, the rise in atomic

mass does not appear to be uniform. It was not possible, therefore, to predict how many

elements could be discovered between two heavy elements.

4. Position of hydrogen : Hydrogen shows

similarity with halogens (group VII). For

example, the molecular formula of

hydrogen is H2

while the molecular

formulae 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

(groupI). There is a similarity in the

molecular formulae of the compounds of

hydrogen alkali metals (Na, K, etc) formed

with chlorine and oxygen. On considering

the above propereties it can not be decided

whether the correct position of hydrogen is

in the group of alkali metals (group I) or in group of halogens