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Question
Compare and contrast the arrangement of elements in Mendeleev’s Periodic Table and the Modern Periodic Table.
Compare and contrast the arrangement of elements in Mendeleev’s Periodic Table and the Modern Periodic Table.
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Solution
About Mendeleev's periodic table:
- Mendeleev’s periodic table is an arrangement of elements in an increasing atomic mass order in a tabular form, such that it reflects similarities and trends in the behavior of elements.
- Mendeleev initially arranged elements, one below the other, in the order of increasing atomic weight. Elements having similar properties are placed nearby. Elements with similar properties are found in the same horizontal row.
About the modern periodic table:
- Modern periodic law states that “the physical and chemical properties of elements are the periodic functions of their atomic numbers”.
Henry Moseley was the scientist who started the modern periodic law. He found that atomic number is a better fundamental property of elements compared to atomic mass. - The vertical columns in the periodic table are called groups and the horizontal rows are called periods. The modern periodic table has eighteen groups and seven periods.
Mendeleev’s Periodic Table Modern Periodic Table The elements are arranged in the increasing order of their atomic masses. The elements are arranged in the increasing order of their atomic numbers. The physical and chemical properties of elements are a periodic function of their atomic masses. The physical and chemical properties of elements are the periodic functions of their atomic numbers There are 8 groups. Each group is subdivided into sub-group ‘a’ and ‘b’ There are 18 groups. Groups are not subdivided into sub-groups. Groups for Noble gas were not present as noble gases were not discovered by that time. A separate group is meant for noble gases. There was no place for isotopes. This problem has been rectified as slots are determined according to atomic number.
About Mendeleev's periodic table:
- Mendeleev’s periodic table is an arrangement of elements in an increasing atomic mass order in a tabular form, such that it reflects similarities and trends in the behavior of elements.
- Mendeleev initially arranged elements, one below the other, in the order of increasing atomic weight. Elements having similar properties are placed nearby. Elements with similar properties are found in the same horizontal row.
About the modern periodic table:
- Modern periodic law states that “the physical and chemical properties of elements are the periodic functions of their atomic numbers”.
Henry Moseley was the scientist who started the modern periodic law. He found that atomic number is a better fundamental property of elements compared to atomic mass. - The vertical columns in the periodic table are called groups and the horizontal rows are called periods. The modern periodic table has eighteen groups and seven periods.
| Mendeleev’s Periodic Table | Modern Periodic Table |
| The elements are arranged in the increasing order of their atomic masses. | The elements are arranged in the increasing order of their atomic numbers. |
| The physical and chemical properties of elements are a periodic function of their atomic masses. | The physical and chemical properties of elements are the periodic functions of their atomic numbers |
| There are 8 groups. Each group is subdivided into sub-group ‘a’ and ‘b’ | There are 18 groups. Groups are not subdivided into sub-groups. |
| Groups for Noble gas were not present as noble gases were not discovered by that time. | A separate group is meant for noble gases. |
| There was no place for isotopes. | This problem has been rectified as slots are determined according to atomic number. |
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