number of iodine protons
Iodine Half-Life Experiment. Iodine is element number 53. That is, Iodine has 53 protrons and 53 electrons. That is what determines that it is Iodine. We could also say that for Iodine, Z = 53. How many neutrons does Iodine have? Most naturally-occuring Iodine is Iodine-127. We could say A = 127. Remember, A is the atomic mass number of an isotope -- the total number of nucleons inside the nucleus. A is the total number of the protons and neutrons inside the nucleus, A = Z + N. N = A - Z. N = 127 - 53. N = 74. Most naturally-occuring Iodine has 74 neutrons. We can write this as. 127 I 53. What happens if this naturally-occuring Iodine-127 absorbs a neutron?