A neutral parent atom has mass 210.0200 u. After α-decay, the neutral daughter atom and helium atom have masses 206.0120 u and 4.0026 u respectively. Take 1 u·c² = 931.5 MeV. The Q-value is closest to:
Options

Question

A neutral parent atom has mass 210.0200 u. After α-decay, the neutral daughter atom and helium atom have masses 206.0120 u and 4.0026 u respectively. Take 1 u·c² = 931.5 MeV. The Q-value is closest to:

Options

G1 Physics · Accepted Answer

For α-decay with neutral atomic masses, Δm = M(parent)−M(daughter)−M(He). Substitute: Δm = 210.0200−206.0120−4.0026 = 0.0054 u. Therefore, Q = 0.0054×931.5 = 5.0301 MeV. So the closest option is 5.0 MeV. Correct option: B.