What are the fixed distances from the nucleus.?

The fixed distances from the nucleus refer to the specific energy levels or orbitals where electrons are likely to be found around an atom's nucleus. These distances correspond to quantized energy states dictated by quantum mechanics, typically represented as principal quantum numbers (n). For example, in hydrogen, these distances increase with higher energy levels, with electrons occupying distinct shells or orbitals at defined distances from the nucleus. Each shell can hold a certain number of electrons, and the arrangement of these shells determines the atom's chemical properties.