1. Alpha Decay (α-Decay):

In alpha decay, a radioactive element emits an alpha particle, which consists of two protons and two neutrons bound together as a helium nucleus (α-particle). When an alpha particle is emitted, the parent nucleus loses two protons and two neutrons. This results in a decrease of the atomic number (Z) by two and a decrease of the mass number (A) by four units.

2. Proton Emission:

Proton emission is a relatively rare type of radioactive decay in which a proton is directly emitted from the nucleus. This occurs when the nucleus is in an excited state and has an excess of protons compared to neutrons. The emission of a proton results in a decrease of the atomic number (Z) by one unit while the mass number (A) remains unchanged.

3. Spontaneous Fission:

Spontaneous fission is a process in which a heavy, unstable nucleus splits into two or more smaller nuclei. During spontaneous fission, the parent nucleus breaks into fragments of similar masses, releasing a significant amount of energy. This process involves the loss of several protons and neutrons from the original nucleus, resulting in the formation of new elements with lower atomic numbers.

4. Cluster Decay:

Cluster decay is a phenomenon where a radioactive nucleus emits a cluster of protons and neutrons, known as a cluster, instead of a single particle. The emitted cluster can be a group of protons, neutrons, or a combination of both. Cluster decay results in the loss of multiple protons and neutrons, leading to changes in the atomic number (Z) and mass number (A) of the parent nucleus.

5. Double Proton Emission:

In some cases, a highly excited nucleus can undergo double proton emission, where two protons are emitted simultaneously. This rare decay process reduces the atomic number (Z) by two units while leaving the mass number (A) unchanged.