ng are the defects in the Mendeleev periodic table:Anomalous PairsThe following pairs of elements don’t follow the follow Mendeleev’s PRINCIPLES:Cobalt (58.9) with a higher ATOMIC mass precedes Nickel (58.6) in the periodic table.Tellurium (127.6) with a higher atomic mass than Iodine (126.9) precedes it in the periodic table.Grouping of chemically dissimilar elementsElements such as Copper and Silver bear no resemblance with the alkali metals, but they have been PLACED together in the first group.Position of IsotopesAccording to Mendeleev’s Periodic Law, isotopes of an element must be given separate places in the periodic table because they have different atomic masses.Electronic arrangementIt does not explain the electronic arrangement of elements.Separation of chemically similar elementsElements that are chemically similar such as Gold and Platinum have been placed in separate groups.The position of hydrogenHydrogen was not given a fixed position because it was considered in Group IA as well as in Group VIIA.hope this will HELP