Chapter 10 - Nuclear Chemistry - Problems - Page 343: 10.2

For each isotope give its: [1] atomic number; [2] mass number; [3] number of protons; [4] number of neutrons. a. $^{85}_{38}Sr$ used in bone scans Atomic Number: 38 Mass Number: 85 Number of Protons: 38 Number of Neutrons: 85-38 = 47 b. $^{67}_{31}Ga$ used in abdominal scans Atomic Number: 31 Mass Number: 67 Number of Protons: 31 Number of Neutrons: 67-31 = 36 c. Selenium-75 used in pancreas scans Atomic Number: 34 Mass Number: 75 Number of Protons: 34 Number of Neutrons: 75-34 = 41

For a and b, The value given at the lower left of the element symbol is the atomic number. The value given at the upper left of the element symbol is the mass number. Atomic number = number of protons. Number of neutrons = mass number - number of protons. For c, The value given in the question is the mass number(75). Find the atomic number from the periodic table. Atomic number = number of protons. Number of neutrons = mass number - number of protons.