compare and contrast the arrangement of elements in mendeleev's periodic table and the modern periodic table......plz answer
Answers
Mendeleev's periodic table-
> Elements are arranged in the increasing order of their atomic masses.
> There are 8 Groups.
> Each groups are subdivided into sub group 'a' and 'b'
> Groups for Noble gas was not present as noble gases were not discovered by that time.
> There was no place for isotopes.
Modern periodic table -
> Elements are arranged in the increasing order of their atomic numbers.
> There are 18 Groups.
> Groups are not subdivided into sub-groups.
> A seprate group is meant for noble gases.
> This problem has been rectified as slots are determined according to atomic number.
Difference between Mendeleev's and modern periodic table are :
1.In Mendeleev's periodic table elements are arranged in order of increasing atomic masses but in Modern Periodic Table elements are arranged according to increasing atomic number.
2. In Mendeleev's periodic table there are 8 groups and 6 periods
Where as in Modern Periodic table there are 18 groups and 7 periods.
3. In Mendeleev periodic table position of hydrogen and isotopes are not specified where as in Modern Periodic Table the position of hydrogen and isotopes are specified.
4. Mendeleev's periodic law states that the elements are the periodic function of their atomic masses where as modern periodic law states that the elements are the periodic function of their atomic numbers.
5. Lanthanoids and actinoids are at the bottom in periodic table where as in Mendeleev periodic table they were not present.
6. In Modern Periodic Table noble gases occupy group 18 Whereas in Mendeleev's periodic table noble gas was not present.
7. Transition metals were placed along with Representative elements in Mendeleev periodic table was in Modern Periodic Table transition metals are in centre of periodic table where as Representative elements are at left and right of the periodic table.
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