Which statement correctly describes gamma decay?

• A. Releases gamma rays without changing the number of neutrons or protons.
• B. Changes the neutron number but not the proton number.
• C. Produces alpha particles.
• D. Changes the proton number.

Answer: (A)

Gamma decay is a process where the nucleus drops to a lower energy state by emitting a gamma photon, a high-energy electromagnetic wave. This emission carries away the excess energy but does not involve removing or adding any nucleons, so the numbers of protons and neutrons—the atomic number and mass number—remain the same. That’s why gamma decay does not change the proton number or the neutron number. It’s different from alpha decay, which ejects a helium nucleus and changes both Z and A, and from beta decay, which changes Z (and thus the element) by converting a neutron to a proton or vice versa. Gamma decay often occurs after a nucleus has been left in an excited state by a prior decay, as a final step to reach the ground state. Internal conversion is related but involves ejecting an orbital electron instead of emitting a gamma ray, while still leaving Z and A unchanged.