Question

defects in the mandeleev periodic table​

Answer 1

The following pairs of elements did not follow Mendeleev'sPrinciples:

Cobalt (58.9) with higher atomic mass precedes Nickel (58.6) in the periodic table. Tellurium (127.6) with higher atomic mass than Iodine (126.9) is also placed before it in theperiodic table.....

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Answer 2

Mandeleev Periodic Table

• Hydrogen was like an alkali metal who can give electrons but like an halogen it occurs in diatomic form and form covalent bonding with non metals.

• Due to this, finally Mandeleev wasn't able to assign correct position to hydrogen.

• Since Mandeleev had designed periodic table according to atomic masses. As a result, a question of Isotope arrived that why then isotopes aren't given position at that table.

• Also, due to same base of atomic masses,  he was wasn't able to correctly give positions to some metals.