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How were the positions of the elements Co and Ni resolved in the modern periodic table?

Discussion in 'CBSE Class 10 Chemistry Help' started by phani, Jan 13, 2012.

1. phaniMemberStaff Member

How were the positions of the elements Co and Ni resolved in the modern periodic table?

On the basis of atomic masses, Ni (58.7) should be placed before Co (58.9). This was defect in Mendeleev’s table because the element Co was placed before Ni. However, the atomic number of Co Z = 27) is less than that of Ni (Z 28). Therefore, they have been correctly arranged in the modern periodic table.