How proton and neutron survive in nucleus?

Answer 1

There are four fundamental forces in particle physics: electromagnetism, gravity, the strong nuclear force, and the weak nuclear force. The strong nuclear force is mediated by a particle called the gluon (like electromagnetism is mediated by the photon). Protons and neutrons are not elementary particles. They are composed of two types of quarks, up and down, with charges of +2/3 and -1/3 respectively. Quarks are bound to eachother by electromagnetism but, more importantly, also by the strong nuclear force. So the strong nuclear force is responsible for holding together the protons and neutrons themselves. The gluons then bind protons and neutrons together indirectly through exchanging composite particles called pions, made of two quarks held together by gluons.