Final answer:
The question involves completing a balanced nuclear equation for the decay of protactinium-231, resulting in iridium-192 and an alpha particle. The type of decay is alpha decay, not fission or fusion.
Step-by-step explanation:
The student is asking about the type of nuclear reaction and to complete a nuclear reaction equation involving protactinium-231 (231 Pa). In nuclear reactions, it is essential to maintain the balance of mass numbers (superscripts) and atomic numbers (subscripts). The question implies that protactinium-231 undergoes a nuclear reaction, producing iridium-192 (192 Ir) and another particle yet to be identified.
To balance the nuclear equation, consider that the sum of the mass numbers and the atomic numbers before and after the reaction must be equal. Since 231 Pa has a mass number of 231 and an atomic number of 91, and 192 Ir has a mass number of 192 and an atomic number of 77, the missing particle needs to balance the equation by having a mass number of 39 (231-192) and an atomic number of 14 (91-77), which corresponds to an alpha particle (4 He).
The complete balanced nuclear reaction is:
231 Pa -> 192 Ir + 4 He
Given that an alpha particle is emitted in the reaction, this is a type of radioactive decay known as alpha decay, which is neither fission nor fusion.