Why are protons present in the center and are they not pulled outside by the electrons as both are oppositely charged with the same unit of charge?

 Protons are heavy with a mass of 1 unit and hence are concentrated in the centre

of the atom. The mass of electrons is negligible i.e.1/1800 times less than that of protons. Hence, Electrons are not able to attract the protons and pull them out of the nucleus, although their charge is of the same value.