Researchers study an unknown radionuclide X and observe that each decay event has the following characteristics:
• The mass number of the nucleus remains unchanged.
• The atomic number increases by exactly one unit.
• An electron with kinetic energy near 0.6MeV is detected.
• No positrons are detected.
Assume conservation of electric charge, nucleon number, and lepton number applies in each event.
(a) Based on the observations, identify the decay mode exhibited by nuclide X.
(b) Write a general nuclear equation for one such decay transforming ZAX into its daughter Z+1AY, explicitly including all emitted particles.
(c) If A=137 and Z=55 for the parent, give the nuclide symbol for the daughter produced in a single decay.
(d) Although no neutral particles are directly detected, use charge and lepton-number conservation to argue that an additional electrically neutral particle must be emitted in every decay event.