Valence is a concept in nuclear physics, based on the nuclear shell model, referring to the state or characteristic of nucleons (protons and neutrons) occupying the outermost energy shells within an atomic nucleus. It investigates the influence of these outer nucleons on fundamental nuclear properties, structure, stability, and reaction behavior. Its significance lies in providing a crucial framework for understanding and predicting nuclear phenomena essential for nuclear energy, astrophysics, and fundamental nuclear research.