how could the modern periodic table remove various anomalies of Mendeleev periodic table
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13
1. Position of Hydrogen:
As they show properties of both metal and non metal (group 1 and 17), Mendeleev was confused in placing the element. But in Modern periodic table as it's atomic no is 1, it is placed in the first group.
2. Position of Isotopes:
As Mendeleev arranged elements in the basis of increasing atomic masses, the position of isotopes were a major barrier. But in Modern periodic table, as elements are arranged in the increasing atomic no there is no problem in arranging isotopes as atomic masses are not required.
3. Anomalous pair of elements:
As the Mendeleev law states that "elements are arranged in increasing atomic masses", placing of heavier elements before lighter elements was a controversy (ex cobalt(atomic mass - 58.9) was placed before nickel(atomic mass - 58.7)). But as Modern periodic law states that "elements are arranged in increasing atomic no", there was no problem in placing cobalt and nickel based on their properties.
4. Positioning of Transition metals:
Transition metals in Mendeleev periodic table are not arranged properly they are only arranged to suit the valencies for ex:Li, Na, K have quite different properties than Ag, Au they were arranged in same group yet they have differing property. But in modern periodic table the transition elements were placed correctly (by centre) accordingly to their properties and valencies it resolved the problem.
5. Noble gases:
As these noble gases were discovered later, they were arranged in a different group without disturbing the Mendeleev's arrangement but however the Mendeleev's table was revised it did not disturb the arrangement at most.
: ) Hope this Helps !!!
As they show properties of both metal and non metal (group 1 and 17), Mendeleev was confused in placing the element. But in Modern periodic table as it's atomic no is 1, it is placed in the first group.
2. Position of Isotopes:
As Mendeleev arranged elements in the basis of increasing atomic masses, the position of isotopes were a major barrier. But in Modern periodic table, as elements are arranged in the increasing atomic no there is no problem in arranging isotopes as atomic masses are not required.
3. Anomalous pair of elements:
As the Mendeleev law states that "elements are arranged in increasing atomic masses", placing of heavier elements before lighter elements was a controversy (ex cobalt(atomic mass - 58.9) was placed before nickel(atomic mass - 58.7)). But as Modern periodic law states that "elements are arranged in increasing atomic no", there was no problem in placing cobalt and nickel based on their properties.
4. Positioning of Transition metals:
Transition metals in Mendeleev periodic table are not arranged properly they are only arranged to suit the valencies for ex:Li, Na, K have quite different properties than Ag, Au they were arranged in same group yet they have differing property. But in modern periodic table the transition elements were placed correctly (by centre) accordingly to their properties and valencies it resolved the problem.
5. Noble gases:
As these noble gases were discovered later, they were arranged in a different group without disturbing the Mendeleev's arrangement but however the Mendeleev's table was revised it did not disturb the arrangement at most.
: ) Hope this Helps !!!
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What about transition metals and noble gasses??
I will clear ur doubt
Transition metals in mendeleev periodic tables are not arranged properly they are only arranged to suit the valencies for ex:Li, Na, K have quite different properties than Ag, Au they were arranged in same group yet they have differing property. But in modern periodic table the transition elements were placed correctly (by centre) accordingly to their properties and valencies it resolved the problem.
As these noble gases were discovered later, they were arranged in a different group without disturbing the Mendeleev's arrangement but however the Mendeleev's table was revised it did not disturb the arrangement at most.
hope u r clear now tanlann
Answered by
25
(a) In the Modern Periodic table elements are arranged in the increasing order of their atomic number. This removes the anomaly regarding certain pairs of elements in Mendeleev’s periodic table.
(b) Atomic number of cobalt is 27 and nickel is 28. Hence, cobalt will come before nickel even though its atomic mass is greater.
(c) All isotopes of the same elements have different atomic masses, but same atomic number; therefore they are placed in the same position in the modern periodic table.
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