Question

 In the modern Periodic Table, why does cobalt with higher atomic mass of 58.93 appear before nickel having lower atomic mass of 58.71?

Answer 1

In the modern periodic table, elements are arranged according to their increasing atomic number. The atomic numbers of cobalt (Co) and nickel (Ni) are 27 and 28, respectively. Therefore, although cobalt (Co) has higher atomic mass, it appears before nickel (Ni) in the periodic table.