Question

An unstable isotope with mass number210 emits 5.3MeV alpha particle. If the atomic mass of unstable isotope is 209.98 u and alpha particle is 4.0026u, determine the atomic mass of daughter nuclide. 

Answer 1

$_{84}^{210}Po\to _2^4He+_{82}^{206}Pb,$

$E=(m_{Po}-m_{He}-m_{Pb})c^2,$

$m_{Pb}=m_{Po}-m_{He}-\frac E{c^2}=205.9745~u.$