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How is the problem regarding the position of cobalt (59CO) and nickel (59Ni) in Mendeleev’s periodic table resolved in modern periodic table? |
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Answer» Mendeleev arranged the elements in their increasing order of atomic masses. But some elements with higher atomic masses are placed before those having lower atomic masses, e.g. cobalt (CO) with atomic mass 58.93 is placed before nickel (Ni) having atomic mass 58.71. Moderm periodic table was prepared on the basis of the atomic number of elements. The atomic number of CO is 27 and that of Ni is 28. So nickel is placed after cobalt. |
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