Bohr radius

The Bohr radius is a fundamental constant in physics that measures the approximate distance between the nucleus of an atom (like the nucleus of a hydrogen atom) and its outermost electron in its lowest energy state. Think of it as the typical size of a hydrogen atom, roughly 0.53 nanometers—much smaller than a virus but larger than individual atoms. This value helps scientists understand atomic structure, predict how atoms interact, and develop models for chemical behavior. It essentially provides a scale for the size of atomic systems in quantum mechanics.