Question

State defects of Mendeleev's periodic table.

Answer 1

1. Anomalous pair: Some pairs of elements didn't follow Mendeleev's principles. Argon with an atomic mass of 39.9 precedes potassium with an atomic mass of 39.1. Cobalt with an atomic mass of 58.9 precedes nickel with an atomic mass of 58.6. Tellurium with an atomic mass of 127.6 precedes iodine with an atomic mass of 126.9.
2. Position of isotopes: According to Mendeleev's periodic law. isotopes of an element must be given separate places in the periodic table since they have different atomic masses. But they were assigned to separate places.
3. Grouping of chemically dissimilar elements: Copper and silver are placed in the first group, but they have no resemblance to alkali metals.
4. Separation of chemically similar elements: Gold and platinum are chemically similar, but they are placed in separate groups.
5. It does not explain the electron arrangement.
6. Not given a particular position for hydrogen.