What happens to the nucleus during radioactive decay?

During radioactive decay, the nucleus of an unstable atom undergoes a transformation that alters the ratios of neutrons to protons, which is essential for achieving stability. This process can take various forms, such as alpha decay, beta decay, or gamma decay, depending on the type of particle emitted or the energy released during the decay.

In alpha decay, for instance, the nucleus loses two protons and two neutrons, effectively splitting off a helium nucleus. In beta decay, a neutron is transformed into a proton (or vice versa), which changes the atomic number of the element and thus alters the overall composition of the nucleus. These changes help the nucleus to move towards a more stable state.

The other options do not accurately represent the processes occurring during radioactive decay. While splitting into smaller atoms reflects a part of alpha decay, it doesn't encompass all forms of decay. Gaining electrons is not a mechanism of stability for the nucleus, as stability is achieved through the neutron-proton balance and not through electron acquisition. Similarly, suggesting that the nucleus 'simply vanishes' disregards the fundamental principle of conservation of mass and energy; it transforms rather than disappears. Thus, option C provides the most accurate description of the nucleus's behavior during radioactive decay.