Alpha, beta, gamma decay

Radioactivity is a phenomenon in which unstable atomic nuclei release energy by emitting radiation. The concept of radioactivity is fundamental to understanding the processes that occur within an atom, particularly with regard to its nucleus. There are three main types of radioactive decay: alpha decay, beta decay, and gamma decay. Each type of decay involves different particles and energies that can transform the parent nucleus into a different element or isotope. The purpose of this lesson is to explain alpha, beta, and gamma decay in detail.

Alpha decay

Alpha decay is a type of radioactive decay in which an unstable nucleus emits an alpha particle. An alpha particle is composed of two protons and two neutrons, making it similar to the nucleus of a helium-4 atom. This type of decay is common in heavier isotopes.

^{A}_{Z}X rightarrow ^{A-4}_{Z-2}Y + ^{4}_{2}alpha

Here, X represents the original nucleus before decay, which has atomic number Z and mass number A. After emitting an alpha particle, it transforms into a new element Y having atomic number Z-2 and mass number A-4.

Example: Uranium-238 undergoes alpha decay to form thorium-234:

^{238}_{92}U rightarrow ^{234}_{90}Th + ^{4}_{2}alpha

In this process the uranium nucleus loses two protons and two neutrons and turns into thorium.

Beta decay

Beta decay is a process by which a beta particle (electron or positron) is emitted from the nucleus. It can occur in two forms: beta-minus decay and beta-plus decay.

Beta-minus decay

In beta-minus decay, a neutron turns into a proton, and an electron and antineutrino are emitted. The formula representing this decay is:

^{A}_{Z}X rightarrow ^{A}_{Z+1}Y + e^- + overline{nu}_e

The atomic number increases by 1, resulting in the transformation of the element into another element, while the mass number remains unchanged.

Example: Carbon-14 undergoes beta-minus decay to form nitrogen-14:

^{14}_{6}C rightarrow ^{14}_{7}N + e^- + overline{nu}_e

A neutron in the carbon nucleus is transformed into a proton, and an electron (beta particle) and an antineutrino are emitted.

Beta-plus decay

In beta-plus decay, a proton turns into a neutron, and a positron and neutrino are emitted. The formula is:

^{A}_{Z}X rightarrow ^{A}_{Z-1}Y + e^+ + nu_e

The atomic number decreases by 1, leading to the formation of a new element, but the mass number remains constant.

Example: Sodium-22 undergoes beta-plus decay to form neon-22:

^{22}_{11}Na rightarrow ^{22}_{10}Ne + e^+ + nu_e

A proton in the sodium nucleus converts into a neutron, releasing a positron and a neutrino.

Gamma decay

Gamma decay occurs when an unstable nucleus emits energy in the form of high-frequency electromagnetic waves, called gamma rays. Unlike alpha and beta decay, gamma decay does not involve the conversion of one element into another. It usually follows other types of decay, such as alpha or beta decay, which is a way for the daughter nucleus to release excess energy.

^{A}_{Z}X^* rightarrow ^{A}_{Z}X + gamma

The symbol X^* denotes the excited parent nucleus before gamma decay. The nucleus does not change into another element; it only goes from an excited state to a lower energy state.

Example: Technetium-99m emits a gamma ray and becomes technetium-99:

^{99m}_{43}Tc rightarrow ^{99}_{43}Tc + gamma

m represents a metastable state, a state of higher energy. By emitting a gamma ray the nucleus reaches a more stable energy configuration.

Conclusion

Alpha, beta and gamma decay are essential processes for understanding the stability of atomic nuclei and the transformation of elements into elements with different energies. Alpha decay reduces both mass and atomic number, leading to the formation of a new element. Beta decay results in the conversion of neutrons into protons or vice versa, emitting beta particles in the process, which transform the resulting element. Gamma decay aids in energy stabilization by emitting electromagnetic radiation, without changing the element itself. These processes are not only important for academic discoveries, but have practical applications in medical imaging, power generation, radiation therapy and much more, which form the cornerstone of nuclear physics. Through understanding and applying these concepts, we gain insight into both the fundamental building blocks of matter and innovative technological advancements.

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