What determines whether a nucleus is stable or unstable (radioactive)?

The stability or instability of a nucleus is fundamentally based on the balance of forces within the atom, particularly the strong nuclear force and the electromagnetic force. The strong nuclear force acts to hold protons and neutrons together, while electromagnetic force, arising from the repulsion between positively charged protons, works to push them apart. A stable nucleus has a balance between these attractive and repulsive forces, allowing it to maintain its integrity over time.

When the nucleus has too many or too few neutrons relative to protons, or if it is too massive overall, this balance can be disturbed. This leads to radioactive decay as the nucleus seeks to reach a more stable configuration by emitting particles or energy. Therefore, the stability of a nucleus is directly influenced by the interplay of these forces, making the balance of forces in the atom the key factor that determines its stability.

Other choices, while they may relate to certain aspects of nuclear chemistry, do not directly determine nuclear stability. The number of protons affects the identification of the element but does not alone dictate stability without considering neutron counts. Electric charge influences interactions between charged particles but does not reflect the stability of the nucleus. Proximity to other atoms might impact the environment of a nucleus but does not fundamentally change its inherent