E.3.8—Decay equations

Balance alpha decay

Write ${}^{A}_{Z}X\rightarrow{}^{A-4}_{Z-2}Y+{}^{4}_{2}\mathrm{He}$. Check both A and Z on the two sides.

Balance beta decay

For beta-minus use $^{A}_{Z}X\rightarrow{}^{A}_{Z+1}Y+{}^{0}_{-1}e+\bar{\nu}_e$. For beta-plus use $^{A}_{Z}X\rightarrow{}^{A}_{Z-1}Y+{}^{0}_{+1}e+\nu_e$. Gamma emission adds $^{0}_{0}\gamma$ after an excited daughter.

Balance a reaction

Conserve total nucleon number and charge. For uranium-235 absorbing a neutron and producing xenon-140 and strontium-94, the remaining nucleon number identifies the emitted neutrons.

Common trap

Do not omit the neutrino or antineutrino when the syllabus asks for a complete beta-decay equation, and do not balance A while leaving charge unbalanced.