The discovery of radioactive elements was a significant moment in the history of chemistry. The powerful energy released by the radium isotope, for instance, prompted Marie Curie to wonder whether this energy could be harnessed, leading to her discovery of radiation therapy. An understanding of radiation would also change how chemical compounds were thought about and classified.

There are three types of radioactive particles, alpha, beta, and gamma rays. Alpha is the least penetrating type but also one of the most dangerous. Beta is much more penetrating than alpha particles, and gamma rays are more penetrating still.

History

Scientists began to research alpha rays almost as soon as they identified them in 1900. The name alpha comes from the first two letters of the Greek alphabet, α, and β. This was followed by discovering what we now call beta rays in 1904 and gamma-rays in 1896. Since these discoveries, scientists have been studying properties of alpha, beta, and gamma rays at increasingly smaller scales

Properties of Alpha, Beta, and Gamma Rays

Alpha, beta, and gamma rays are all a form of ionizing radiation. Ionizing radiation is energy that can break the chemical bonds in atoms and molecules, causing them to lose their structure (i.e., their atomic or molecular structure) and become charged particles or other excited states. These particles can have a size of 1 to 100 nm and a charge of either +1 e/nucleon or -1 e/nucleon.

  • Alpha Particles:

Alpha particles are emitted during the process of nuclear fission. Alpha particles are emitted from the nucleus of an atom. They consist of two protons and two neutrons bound together. The average speed of alpha particles is around 5% the speed of light; they are generally very large in mass and slow-moving, making them easy to measure but more difficult to navigate around.

Alpha radiation is dangerous because alpha radiation has a very large particle size (10−12 meters), meaning that it can cause significant damage to living tissue. 

  • Beta Particles:

Beta radiation is emitted from the nucleus of an atom and consists of an electron emitted from the electron cloud. Electrons have far less mass than alpha particles, but their charge and speed make them more dangerous. They are about three times faster than alpha radiation, which means they can penetrate deeper into the body before stopping. Beta radiation is dangerous because of the speed at which it travels and the small amount of shielding needed to stop it. It can easily penetrate through the skin and spread through the flesh, giving off energy in a process called ionization along the way.

  • Gamma Rays:

Gamma rays are electromagnetic radiation emitted from the nucleus of an atom that is undergoing or has recently undergone radioactive decay. Gamma rays are the most energetic form of electromagnetic radiation and have the shortest wavelength and highest frequency. Gamma rays are similar to X-rays, but X-rays are a lower energy form of electromagnetic radiation. Because gamma rays have very high energy, they can penetrate thick layers of lead or concrete and travel long distances through air, water, and flesh without losing all their energy.

Differences between Alpha, Beta, and Gamma Rays:

  1. Penetration

  • Alpha particles are the smallest of the three but are very large in mass, making them very slow and easy to stop. Beta particles have less mass than alpha particles, and so they can penetrate further into a substance before they lose all their energy. 

  1. Radiation Damage

  • Each type (Alpha, beta, and gamma rays) has different biological effects and can do different degrees of harm to living cells. Alpha particles are the most dangerous because they are large in mass, travel slowly, and can remove electrons from an atom or molecule. This ionization can disrupt the function of DNA and therefore cause cell death.

  1. Isotopes

  • Each element has different isotopes (e.g., calcium-40), but some isotopes are more commonly used than others. The three types of radioactive particles have different sources in nuclear decay, so they have different isotopes associated with them. Gamma rays are emitted from a nucleus and have the same isotopes as their parent radioisotopes.

  1. Half-life

  • The time it takes for half of the material to decay is called its half-life, depending on which isotope is used. The half-life of an isotope can range from seconds to billions of years. The more stable isotopes have longer half-lives.

  1. Detection

  • Alpha particles are easy to detect because they have a large mass and high charge, so they can cause so much damage to the body. Alpha particle detectors, like Geiger counters, use a scintillation counter to detect ionizing radiation, then convert that information into an audio signal or a visual display. 

Conclusion

Properties of alpha, beta, and gamma rays:

  • Alpha Particles:

Alpha particles are the most dangerous of the three because they are large in mass, travel slowly, and can remove electrons from an atom or molecule. This ionization can disrupt the function of DNA and cause cell death.

  • Beta Particles:

Beta particles are much less damaging than alpha particles because they have less mass and travel faster but still retain a positive charge

  • Gamma Rays:

Gamma rays are the least dangerous because they have the least mass and energy, travel at the fastest speeds, and have no charge.