Radioactive Disintegration

When disintegration occurs, the nuclei release radiation in the form of alpha (α), beta (β) and gamma (γ) particles.

Alpha disintegration

It consists of the emission of the alpha (α) particle. This particle is positively charged, its charge being 2+. It consists of two protons and 2 neutrons expelled from the nucleus.

First Law of Radioactivity / Soddy's Law

“When a nucleus emits an alpha (α) particle, its atomic number decreases two units and its mass number decreases 4 units.”


Beta disintegration

It consists of the emission of beta (β) particles. It is formed by an electron that is "shot" at a very high speed out of the nucleus. In fact, the electron is not in the nucleus. The electron is emitted because of the unstable nucleus.

Second Law of Radioactivity / Soddy-Fajans-Russell Law

“When a nucleus emits a beta (β) particle, its atomic number increases by one and its mass number does not change.”


Remember that the relative electrical charge of the electron is 1-. In this case, the parent atom and the child atom are isobaric. Thorium, cesium and strontium atoms emit β radiation.

Thorium-234, for example, transforms into protactinium-234 by emitting an electron, beta particle.

Gamma disintegration

Gamma emissions (γ) are not particles. They are electromagnetic waves, just like light or light waves.

It has a greater penetration power than alpha and beta. They can cross up to 20cm in steel and 5cm in lead (Pb). For this reason, these emissions are very physiologically dangerous. They can damage living tissue and even kill.

Gamma emission (γ) changes neither atomic number nor mass number. Radio-226, for example, transforms into radon-222, emitting gamma radiation as well as alpha particles.