No, neutrons do not change into protons or electrons as the nucleus gets larger. What happens as a nucleus gets larger is that the repulsive force of the additional *protons* starts to get strong enough to make it more difficult for the nucleus to stay together. Neutrons are neutral and so do not contribute to this effect. As the additional protons all have positive charge, the probability that the nucleus breaks apart increases. This "breaking apart" is called decay, or radioactive decay, and happens for atoms with large numbers of protons in the nucleus. Note: there are *no* electrons in the nucleus, they only swarm around the nucleus, exterior to it, in the "electron cloud" of an atom, sometimes called electron orbital shells (e.g., in a chemistry class).