Cobalt has an atomic number 27 and nickel 28. According to the modern periodic law elements are arranged in the order of increasing atomic number. So

Cobalt has an atomic number 27 and nickel 28. According to the modern

1.	Cobalt has an atomic number 27 and nickel 28. According to the modern periodic law elements are arranged in the order of increasing atomic number. So
Answer» Cobalt is PLACED before Nickel EVEN through their atomic MASSES are not in increasing ORDER...