Question

in mendelee s periodic table elements were in order of decreasing atomic mass at some locations for example co and Ni this not explained by mendelee
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Answer 1

Explanation:

Solution :

In Mendeleev's periodic table, Cobalt (Co) with a higher atomic mass of 58.93 u is placed before nickel (Ni) due to the following reasons

(i) The properties of cobalt are similar to those of rhodium (Rh) and iridium (lr) (same group) and

(ii) The properties of nickel are similar to those of palladium (Pd) and platinum (Pt) (same group).