who discovered the nucleus of an atom

The nucleus of an atom was discovered by Ernest Rutherford in 1911. He conducted the famous gold foil experiment where alpha particles were directed at a thin sheet of gold foil, observing their scattering patterns. From this, he concluded that atoms consist of a small, dense, positively charged nucleus where most of the mass is concentrated, surrounded by electrons at relatively large distances. This discovery disproved the earlier plum pudding model and laid the foundation for modern atomic theory.