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

• Modern periodic table is the table in which the classification of elements ate done based on the modern periodic law, which states that all the physical and chemical properties of an element are the periodic functions of their increasing atomoc mumber.

• The cobalt and nickel are placed in the same slot with column of chlorine and bromine which have very different properties than these element and iron which resembles properties of cobalt and nickle is placed far away in Newland law of octaves. This problem has been resolved by the Modern periodic table by arranging the elements in the order of their atomic number without changing their own places.

• Atomic number of cobalt is 27 and nickel is 28.