AAMC FL Practice Exam 2025 - Free Practice Questions and Study Resources.

During alpha decay, an unstable atomic nucleus releases an alpha particle, which is composed of two protons and two neutrons. This process occurs when an atom's nucleus is too heavy or contains an excess of energy, resulting in the need to lose mass to achieve greater stability. The emission of the alpha particle effectively lowers the atomic number of the original element by two, transforming it into a different element, while also reducing the mass number by four. This release is a fundamental type of radioactive decay often observed in heavier elements, contributing to their path toward stability.

The other particles mentioned—beta particles, antineutrinos, and electrons—are associated with different types of decay processes and do not occur during alpha decay. Thus, identifying the alpha particle as the released entity in this process is crucial to understanding nuclear physics and radioactivity.