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Alpha particles play a key role in radioactive decay, specifically in what is known as alpha decay. Consisting of two protons and two neutrons, they are essentially the same as a helium nucleus. Due to their relatively large mass and positive charge, alpha particles have low penetration power. This means they cannot travel far through materials and can be stopped by a simple sheet of paper or even the outer epidermis of human skin. However, despite their low penetration ability, alpha particles can cause significant damage if ingested or inhaled, as they can then come into direct contact with living tissues. Their inability to penetrate deeply makes them less of a threat as an external hazard but more concerning as an internal one.

Beta particles are another type of radiation involved in radioactive decay, but they differ significantly from alpha particles. They can either be electrons or positrons, which are high-energy and high-speed. During beta decay, these particles are ejected from the nucleus of an atom, transforming it. Beta particles have a greater penetration ability compared to alpha particles. To stop them, a thin layer of material such as aluminum or plastic is usually sufficient.
There are two types of beta particles:

• Negative beta particle (electron)
• Positive beta particle (positron)

Each behaves slightly differently due to their charges; however, the considerations for shielding remain similar. Their capacity to penetrate materials more deeply means they pose a more refined balance of risk between external and internal exposures.

Gamma rays are at the other end of the radiation spectrum, noted for their extremely high energy and penetrating power. Unlike alpha and beta particles, gamma rays are not particles, but rather electromagnetic radiation, akin to very high-energy X-rays. Emitted from the nucleus during gamma decay, they carry no charge and have no mass.
What makes gamma rays particularly notable is their ability to penetrate most materials. Consequently, their powerful penetration makes them more challenging to shield against compared to alpha or beta particles. Thick layers of dense materials like lead or concrete are generally required to attenuate gamma rays. This degree of penetration means gamma rays are a significant concern for both external and internal radiation exposure, with their impact only mitigated by specialized and robust shielding solutions.