Are neutrons inside or outside the nucleus?
Neutrons are NUCLEAR particles.
Together with protons, positively charged nuclear particles, protons and neutrons together comprise the nuclear core of an element. Interactions between these particles comprise the strong nuclear force, an attractive force, which at short ranges is strong enuff to overcome the electrostatic repulsion that exists between LIKE electronic charges. For more details, you are going to have to consult a physicist. This is the chemistry section.