What causes nuclear instability?

The nucleus of an atom is composed of protons and neutrons, which are tightly bound together by a strong nuclear force. Despite this, the electromagnetic force causes repulsion between the protons, attempting to tear the nucleus apart. Stability in the nucleus is a delicate balance, and it can be disrupted, leading to instability when:

• The neutron count is excessively high,
• The neutron count is insufficient,
• The total count of nucleons (protons and neutrons) becomes overly large, rendering the nucleus too hefty,
• An overabundance of energy is present within the nucleus.

Modes of radioactive decay

To achieve a stable state, unstable nuclei may undergo several types of spontaneous radioactive decay processes:

• β^- decay - involves a neutron transforming into a proton, during which an electron and an antineutrino are emitted.
• β⁺ decay -sees a proton converting into a neutron, with the emission of a positron and a neutrino.
• α decay - entails the emission of an α particle, which is essentially a helium nucleus. These decay processes help to lower the nucleus's energy, adjust the number of nucleons, and modify the neutron-to-proton ratio towards a more stable configuration.

Nuclear stability graph

A nuclear stability graph visually represents the relationship between the number of protons (Z) and the number of neutrons (N) within nuclei.

Interpreting the graph:

• Nuclei that are stable are found along the line of stability.
• Nuclei positioned above the line possess too many neutrons and typically undergo β^- decay to shed the excess.
• Nuclei located below the line have too many protons and are prone to β⁺ decay in order to correct the imbalance.
• Heavier nuclei, situated to the right of the graph, often decay through α emission to reduce their mass.