Alpha Decay

Definition

Alpha decay is a type of radioactive decay where an atomic nucleus emits an alpha particle, which is a helium nucleus consisting of two protons and two neutrons. This process results in the transformation of the original atom into a new element with a lower atomic number.

5 Must Know Facts For Your Next Test

1. Alpha decay occurs in heavy, unstable atomic nuclei, such as those found in uranium, thorium, and radium.
2. The emission of an alpha particle during alpha decay reduces the atomic number of the original element by two and the mass number by four.
3. Alpha decay is a spontaneous process driven by the strong nuclear force, which can overcome the electrostatic repulsion between protons in the nucleus.
4. The energy released during alpha decay is typically around 4-8 MeV (million electron volts), which is relatively high compared to other types of radioactive decay.
5. Alpha particles have a low penetrating power and can be easily shielded by a thin layer of material, such as a sheet of paper or the outer layer of skin.

Review Questions

• Describe the process of alpha decay and how it results in the transformation of one element into another.
  • In alpha decay, an unstable atomic nucleus spontaneously emits an alpha particle, which is a helium nucleus consisting of two protons and two neutrons. This emission causes the original nucleus to lose two protons and two neutrons, effectively transforming it into a new element with a lower atomic number. For example, uranium-238 (U-238) undergoes alpha decay to become thorium-234 (Th-234), reducing the atomic number from 92 to 90 and the mass number from 238 to 234.
• Explain the role of the strong nuclear force in driving the process of alpha decay and how it overcomes the electrostatic repulsion between protons in the nucleus.
  • The strong nuclear force is the dominant force within the atomic nucleus, acting to hold the protons and neutrons together. In heavy, unstable nuclei, the strong nuclear force can overcome the electrostatic repulsion between the protons, allowing the nucleus to emit an alpha particle. This emission reduces the number of protons and neutrons in the nucleus, making the resulting nucleus more stable and less likely to undergo further radioactive decay. The balance between the strong nuclear force and the electrostatic repulsion is a key factor in determining the stability of atomic nuclei and the likelihood of alpha decay.
• Analyze the characteristics of alpha particles emitted during the process of alpha decay and discuss their implications for radiation protection and shielding.
  • Alpha particles emitted during alpha decay are relatively large and heavy, consisting of two protons and two neutrons. Due to their large size and charge, alpha particles have a low penetrating power and can be easily shielded by a thin layer of material, such as a sheet of paper or the outer layer of skin. This low penetrating power means that alpha radiation poses a significant health risk only when the source of radiation is inside the body, such as through ingestion or inhalation. However, when alpha-emitting radioactive materials are outside the body, they can be effectively shielded, and the risk of exposure is greatly reduced. This characteristic of alpha particles is an important consideration in radiation protection and the design of shielding materials for handling radioactive substances.

Related terms

Radioactive Decay: The spontaneous process by which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves.

Nuclear Fission: The splitting of a heavy atomic nucleus, such as uranium or plutonium, into two or more lighter nuclei, accompanied by the release of a large amount of energy.

Radioactive Half-Life: The time it takes for a radioactive substance to decay to half of its original amount.