Question

How.were.the position of the cobalt and nickel resolved in the modern periodic table
.

Answer 1

Explanation:

Mendeleev's Periodic Table was based on the law that the properties of elements are the periodic function of their atomic masses.

So, cobalt with atomic mass 58.93 should be placed after nickel with atomic mass 58.71.

But to maintain similarity in properties, it had to be placed before nickel in Mendeleev's Periodic Table. 

Modern Periodic Table the classification of elements is based on the law that the properties of elements are the periodic function of their atomic numbers.

So, the problem was resolved because cobalt has lower atomic number (27) than that of nickel (28). 

Therefore nickel with atomic number 28 is placed after cobalt with atomic number 27.

 

Answer 2

According to modern periodic law, elements are arranged in the order of increasing atomic numbers. The atomic number of cobalt is 27 and that of nickel is 28. So, in the modern periodic table, cobalt with lower atomic number (27) comes first and nickel with higher atomic number (28) comes later, even if their atomic masses are in the wrong order. In this way, the positions of cobalt and nickel were resolved in the modern periodic table.