Iodine has many isotopes, but only iodine-127 is stable and is found in nature. One

radioactive iodine isotope, I-108, decays by alpha particle emission. Iodine-131 is also radioactive and has many important medical uses.

82 Determine the number of neutrons in an atom of I-127. [1]

83 Explain, in terms of protons and neutrons, why I-127 and I-131 are different isotopes of iodine. [1]

85 Determine the total time required for an 80.0-gram sampleof I-131 to decay until only 1.25 grams of the sample remains unchanged. [1]

Question

Paola Hester

Chemistry

14 November, 07:56

Iodine has many isotopes, but only iodine-127 is stable and is found in nature. One

radioactive iodine isotope, I-108, decays by alpha particle emission. Iodine-131 is also radioactive and has many important medical uses.

82 Determine the number of neutrons in an atom of I-127. [1]

83 Explain, in terms of protons and neutrons, why I-127 and I-131 are different isotopes of iodine. [1]

85 Determine the total time required for an 80.0-gram sampleof I-131 to decay until only 1.25 grams of the sample remains unchanged. [1]

+2

Answers (1)

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Milagros Dillon · Answer 1

Iodine has 53 protons. For question 82, the number 127 stands for neutrons plus protons. So the neutron for I-127 is 74. For 83, according to the definition of isotopes, they need to have the same number of protons and different number of neutrons. I-127 and I-131 satisfy these requirements. For 85, the half life of I-131 is 8 days which means after 8 days, only half of sample remains unchanged. So if 80 gram change to 1.25 gram, it goes through 6 half life. So it took 48 days.