Base your answers
to questions 81 through 85 on the information below.
Iodine has many isotopes, but
only iodine127 is stable and is found in nature. One
radioactive iodine isotope, I108, decays by alpha particle emission.
Iodine131 is also radioactive and has many important medical
uses.
82 Determine the number of neutrons in an atom of I127. [1]
83 Explain, in terms of protons and neutrons, why I127 and I131 are
different isotopes of iodine. [1]
Answer> same atomic number
(protons) but different numbers of neutrons 
84 Complete the equation in your answer booklet for the nuclear decay of
I108. [1]
Link to ANSWER
85 Determine the total time required for an 80.0gram sampleof I131 to
decay until only 1.25 grams of the sample remains unchanged. [1]
