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An alpha particle consists of two protons and two neutrons, resembling a helium-4 nucleus with a two-plus charge. During alpha decay, the parent nuclide emits this alpha particle, reducing the atomic number by two and the mass number by four. For example, polonium-210 converts to lead-206 through alpha decay.

Beta-minus decay converts a neutron into a proton, emitting a high-energy electron and increasing the atomic number by one while keeping the mass number unchanged. Beta-plus decay converts a proton into a neutron, emitting a positron that quickly annihilates with an electron, releasing two 511 keV gamma rays and decreasing the atomic number by one.

Gamma decay occurs when an excited daughter nuclide transitions to its nuclear ground state by emitting gamma radiation, a high-energy electromagnetic quantum. The mass number and atomic number remain unchanged during this process. Gamma emission frequently accompanies other decay modes, such as when cobalt-60 beta decay produces excited nickel-60, which then emits two gamma rays.

Neutron emission is the ejection of a neutron from the nucleus, occurring either spontaneously or in response to bombardment by gamma rays or particles. During neutron emission, the atomic number remains unchanged while the mass number decreases by one. Beryllium-13 decaying to beryllium-12 exemplifies spontaneous neutron emission.

Electron capture occurs when an inner-shell electron combines with a proton in the nucleus, converting it into a neutron. This process decreases the atomic number by one without changing the mass number. The vacancy left by the captured electron is filled by an outer electron, which emits energy typically in the form of X-rays corresponding to the electron transition.

Gamma radiation has the greatest penetration power and passes through most materials, while alpha particles, being the most massive nuclear particles, have very low penetration ability. Neutrons and beta particles fall between these extremes and can be blocked effectively by relatively lightweight materials.

Radionuclides emit six fundamental types of nuclear particles and radiation: alpha particles, beta particles, positrons, neutrons, gamma rays, and X-rays. These emissions occur as radionuclides disintegrate to daughter nuclides through various decay processes. Understanding these emissions is essential for studying radioactive decay and radiometric dating applications.