The fallout from a nuclear explosion and the waste from a nuclear reactor contain radioactive isotopes. For example, iodine-131 (a fission byproduct) is radioactive while iodine-127 (normal iodine) is not. An atom of iodine-131 differs from an atom of iodine-127 because the iodine-131 atom has more
A) protons in its nucleus.
B) gamma rays in its nucleus.
C) electrons in its orbitals.
D) neutrons in its nucleus.

Question

Quizplus · Accepted Answer

Iodine-131 differs from iodine-127 due to having more neutrons in its nucleus. Both isotopes have the same number of protons (since they are both iodine), but their mass numbers differ because of the different number of neutrons.

The Fallout from a Nuclear Explosion and the Waste from a Nuclear