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 occurs in heavy, unstable nuclei as a means of achieving a more stable configuration.

5 Must Know Facts For Your Next Test

1. Alpha decay reduces the mass number of the parent nucleus by 4 and the atomic number by 2, resulting in a new element two places lower on the periodic table.
2. The emitted alpha particle has a positive charge of +2 and a mass of 4 atomic mass units.
3. Alpha decay is common in heavy, neutron-rich nuclei, such as those found in the actinide series of the periodic table.
4. The energy released during alpha decay is typically in the range of 4-8 MeV (million electron volts), which is relatively high compared to other types of radioactive decay.
5. Alpha decay is a spontaneous process and occurs without the need for external energy input, as the parent nucleus is inherently unstable.

Review Questions

• Explain how alpha decay affects the composition of the parent nucleus and the resulting daughter nucleus.
  • During alpha decay, the parent nucleus emits an alpha particle, which is a helium nucleus consisting of two protons and two neutrons. This reduces the mass number of the parent nucleus by 4 and the atomic number by 2, resulting in a new element that is two places lower on the periodic table. The daughter nucleus has a lower mass and a different elemental identity compared to the parent nucleus, as it has lost the alpha particle.
• Describe the role of nuclear stability in the occurrence of alpha decay.
  • Alpha decay is a common process in heavy, neutron-rich nuclei because these nuclei are inherently unstable and tend to be radioactive. The emission of an alpha particle allows the nucleus to achieve a more stable configuration by reducing its mass and charge. The energy released during alpha decay, typically in the range of 4-8 MeV, is a key indicator of the instability of the parent nucleus and the driving force behind this type of radioactive decay.
• Analyze how the information provided about alpha decay can be used to write balanced nuclear equations.
  • $$^{A}_{Z}X \rightarrow ^{A-4}_{Z-2}Y + _{2}^{4}\alpha$$ The general form of a balanced nuclear equation for alpha decay shows that the parent nucleus (X) with mass number A and atomic number Z decays into a daughter nucleus (Y) with a mass number 4 less and an atomic number 2 less, along with the emission of an alpha particle (α). This equation accurately represents the changes in the composition of the nucleus during the alpha decay process, allowing for the prediction and description of this type of radioactive transformation.

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 Stability: The ability of a nucleus to remain unchanged over time, without undergoing radioactive decay or other nuclear transformations.

Nuclear Equations: Equations that represent the changes in the composition of atomic nuclei during nuclear reactions, such as radioactive decay.