Find the Q-value and the kinetic energy of the emitted α-particle in the α-decay of (a) 22688Ra and (b) 22086Rn

Given m (22688Ra) = 226.02540 u, m (22286Rn) = 222.01750 u,


m (22286Rn) = 220.01137 u, m (21684Po) = 216.00189 u.


a) Q value of emitted α particle = (Total Initial mass-Total final mass) × c2

The α particle decay of 226Ra88 is given by:



Hence the Q value will be = [226.02540-(222.01750 + 4.002603)] × c2


= 0.005297 u × c2


= 0.005297 × 931.5 Mev


= 4.94MeV


Kinetic energy is given by =


× 4.94 Mev


= 4.85 MeV


b) Similarly, the decay of 220Rn86 is given by :



Hence, Q value = [220.01137-(216.00189 + 4.0026)]u × c2 = 0.00688u × 931.5 MeV = 6.41MeV


Kinetic energy =


= 6.41 × MeV


= 6.293 MeV


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