Radioactive decay

Radioactive decay is a process by which unstable nuclei become more stable by emitting radiation. This section will explore the types of radioactive decay, their effects on the nucleus, and the use of decay equations to represent nuclear changes.

Radioactive isotopes

Isotopes of an element have the same number of protons but different numbers of neutrons. Some isotopes are radioactive due to:

• Having too many neutrons, which makes the nucleus unstable.

• The nucleus being too heavy, meaning that there are too many protons and neutrons, causing instability.

Radioactive isotopes emit radiation in order to lose energy and become more stable.

Effects of alpha, beta and gamma emissions

The different types of radioactive decay have varying effects on the nucleus:

• Alpha Decay (α-decay):

  • In alpha decay, the nucleus loses 2 protons and 2 neutrons. This decreases the nucleon number (A) by 4 and the proton number (Z) by 2.

  • The result is a different element that is more stable than the original one.

• Beta Decay (β-decay):

  • In beta decay (β decay), a neutron is converted into a proton and an electron.

  • The electron is emitted as the beta particle, while the proton remains in the nucleus, increasing the proton number (Z) by 1.

  • The result is a different element that is more stable than the original one.

  • Neutron → Proton + Electron

• Gamma Emission (γ-emission):

  • Gamma rays are emitted when the nucleus has excess energy. Unlike alpha or beta decay, gamma decay does not change the atomic number or the mass number.

  • It simply allows the nucleus to release energy and reach a more stable state.

Decay equations using nuclide notation

Decay equations can be used to represent the changes that occur during radioactive decay. These equations use nuclide notation to show the emissions of alpha particles, beta particles, and gamma radiation.

• Nuclide Notation:

Where:

• A is the mass number (number of protons and neutrons).

• Z is the atomic number (number of protons).

• X is the symbol for the element.

For example, in alpha decay, the equation might look like:

This shows that uranium-238 decays to thorium-234 by emitting an alpha particle.

In beta decay, an example equation is: