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Question
Compare and contrast the arrangement of elements in Mendeleev’s periodic Table and the Modern Periodic Table.
Solution
| Mendeleev’s periodic table | Modern periodic table |
| Elements are arranged in the increasing order of their atomic masses. | Elements are arranged in the increasing order of their atomic numbers. |
| There are 8 Groups. | There are 18 Groups. |
| Each groups are subdivided into sub group ‘a’ and ‘b’ |
Groups are not subdivided into sub-groups.
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Groups for Noble gas was not present as noble gases were not discovered by that time.
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A seprate group is meant for noble gases.
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There was no place for isotopes.
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This problem has been rectified as slots are determined according to atomic number.
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A
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B
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