A neutral radioactive atom undergoes α-decay. The measured neutral atomic masses are M(parent) = 226.0254 u, M(daughter) = 222.0176 u and M(He) = 4.0026 u. Take 1 u·c² = 931.5 MeV. The energy released in the decay is closest to:
Options

Question

A neutral radioactive atom undergoes α-decay. The measured neutral atomic masses are M(parent) = 226.0254 u, M(daughter) = 222.0176 u and M(He) = 4.0026 u. Take 1 u·c² = 931.5 MeV. The energy released in the decay is closest to:

Options

G1 Physics · Accepted Answer

When neutral atomic masses are used in α-decay, the electron masses balance automatically because the parent has Z electrons and the daughter plus helium atom together also have Z electrons. Mass converted to energy: Δm = M(parent) − M(daughter) − M(He). Substitute: Δm = 226.0254 − 222.0176 − 4.0026 = 0.0052 u. Therefore, Q = Δm·c² = 0.0052×931.5 MeV = 4.8438 MeV. Thus the released energy is approximately 4.84 MeV. Correct option: B.