RRB Group D 13-Dec-2018 Shift 2 Solved Paper

The total number of neutrons in dipositive zinc ion with mass number 70 -
No. of neutrons = Mass number - Atomic number
Atomic mass of zinc is 70 g
Atomic number of Zinc is 30.
Thus, number of neutrons will be,
No. of neutrons = 70 - 30 = 40