Knowledge of atomic structure has evolved over time. thomson discovered that atoms contain electrons, rutherford discovered that most of the mass of an atom is concentrated in its center, and bohr discovered that electrons orbit the nucleus. taken together, what do these discoveries demonstrate

  J.J. Thompson's plum pudding model was devised after the discovery of electron but before the discovery of the nucleus of the atom. Rutherford, who overturned Thompson's plum pudding model proposed that on his experiment (Rutherford model) he discovered that the atom has a tiny, heavy nucleus, which is named as nucleus of the atom. While the most important properties of atomic and molecular structure was explained using the simple [picture of an atom called the Bohr Model. This model was proposed by Niels Bohr. He also concluded that an atom is a small, positively charged nucleus surrounded by orbiting electrons.   The different theories and discoveries  by the great scientists mentioned above demonstrate the atomic model and composition of atoms.  

Rethink and reinvent