Alpha decay

Nuclear processes

Radioactive decay processes Alpha decay Beta decay Electron capture Gamma radiation Neutron emission Proton emission Spontaneous fission Nucleosynthesis Neutron Capture The R-process The S-process Proton capture: The P-process

In alpha decay an atomic nucleus ejects an alpha particle and transforms into a nucleus with mass number 4 less and atomic number 2 less. For example

²³⁸₉₂U → ²³⁴₉₀Th + ⁴₂He

More usually written as

²³⁸U → ²³⁴Th + α

Note that an alpha particle is a helium nucleus, and that both mass number and atomic number are conserved. Essentially alpha decay can be thought of as nuclear fission where the parent nucleus splits into two daughter nuclei.