Final answer:
Nuclear decay does not require an input of energy as it is a spontaneous process driven by strong nuclear forces. In controlled settings, like nuclear reactors, external catalysts can be used to initiate or speed up the reaction.
Step-by-step explanation:
The statement that an input of energy is required for nuclear decay is generally false. Nuclear decay is a spontaneous process for unstable atoms, meaning they release energy as they change into more stable forms without the need for external energy input. This phenomenon is due to the work done by the strong nuclear forces during the decay process. However, when it comes to fusion reactions, such as combining medium-mass nuclei like iron or cobalt, the statement holds true—external energy is required to overcome the electrostatic repulsion between these nuclei.
In the case of nuclear fission, for example, an unstable atom can decay naturally, potentially over long periods. Yet, to harness energy efficiently, a neutron is often used as a catalyst to initiate the fission in a high-mass atom. While the assumption may be that spontaneous decay is the norm, there are scenarios in controlled settings, such as nuclear reactors, where we do intervene to start a nuclear reaction.
The difference between spontaneous decay and induced reactions is important to distinguish. Nuclear decay is indeed a natural process that doesn't require energy to occur, while human-initiated nuclear reactions, such as in nuclear power plants or weapons, often do.