giving Q = [ m N ( X Z A ) − − m N ( X Z − − 1 A ′ ) − − m e − − m ν ν e ] c 2 . However, in this equation, the electron masses do not cancel, and we are left with Q = [ m ( X Z A ) − − m ( X Z − − 1 A ′ ) − − 2 m e ] c 2 .