Final answer:
Ernest Rutherford discovered the nucleus in 1911 and named the proton in 1920. Protons are positively charged particles in the nucleus of atoms. The neutron was discovered by James Chadwick in 1932, following Rutherford's predictions.
Step-by-step explanation:
The nucleus was first discovered by Ernest Rutherford in 1911 when he proposed a nuclear model of the atom, which described the atom as having a positively charged nucleus containing most of its mass, and electrons located far from the nucleus. Ten years later, in 1920, Rutherford named the positively charged particle in the nucleus of a hydrogen atom as the 'proton'. The discovery of protons was crucial to understanding atomic structure and the composition of matter. However, the existence of another particle in the nucleus was necessary to account for atomic stability. Rutherford predicted the existence of an electrically neutral particle to counteract the repulsive forces between protons. This particle, known as the neutron, was not discovered until 1932 by James Chadwick, a student of Rutherford and later a Nobel Prize laureate in Physics. Chadwick's discovery further clarified the structure of the atom and added significant detail to atomic models. Preceding Rutherford's discovery, in 1886, Eugene Goldstein observed canal rays in a cathode ray tube, which were later understood to be composed of positively charged particles, hinting at the existence of protons prior to Rutherford's formal identification.