Which of the following represents the iodine isotope that contains 74 neutrons?

• A. I-74
• B. I-127
• C. I-131
• D. I-124

Answer: (B)

Verified step by step guidance

1. Recall that the isotope notation I-A represents an iodine atom with a mass number A, where the mass number A is the sum of protons and neutrons in the nucleus.
2. Identify the atomic number of iodine (I), which is the number of protons. For iodine, the atomic number is 53.
3. Use the relationship: number of neutrons = mass number (A) - number of protons (Z). Here, neutrons = A - 53.
4. Set up the equation for 74 neutrons: 74 = A - 53, then solve for A to find the mass number of the isotope with 74 neutrons.
5. Compare the calculated mass number A with the given isotope options (I-74, I-127, I-131, I-124) to determine which isotope corresponds to 74 neutrons.