Final answer:
Key contributors to atomic theory include Ernest Rutherford who proposed the nuclear model, J.J. Thomson who discovered the electron, Niels Bohr who developed the Bohr model, and James Chadwick who discovered the neutron.
Step-by-step explanation:
The major contributors to our understanding of the atom and their significant scientific achievements are foundational to modern chemistry and physics. Ernest Rutherford was instrumental in proposing the nuclear model of the atom after his gold foil experiments revealed that atoms have a dense nucleus. J.J. Thomson discovered the electron, which led to the Plum Pudding Model, suggesting that atoms are composed of smaller parts with charges. Niels Bohr refined atomic understanding with the Bohr model, placing electrons in specific energy levels around the nucleus. Finally, James Chadwick discovered the neutron, adding another piece to the structure of the atom and allowing for a better understanding of atomic mass and the behavior of elements.
Scientific Achievement: Discovered the neutron. In 1932, Chadwick confirmed the existence of the neutron, a neutral subatomic particle located in the nucleus of an atom. This discovery was crucial for understanding atomic structure and the stability of atomic nuclei.
These scientists played pivotal roles in advancing our understanding of the atom, and their contributions laid the groundwork for further developments in atomic theory and the field of quantum mechanics.