Explanation:

- Option 1: Rutherford

- Ernest Rutherford is known for discovering the atomic nucleus through his gold foil experiment.

- He proposed the nuclear model of the atom but did not discover neutrons.

- Option 2: Chadwick

- James Chadwick discovered the neutron in 1932.

- His work provided a new understanding of atomic structure.

- Option 3: Bohr

- Niels Bohr is known for the Bohr model of the atom.

- He introduced the concept of electron orbits but wasn't involved in neutron discovery.

- Option 4: Millikan

- Robert Millikan is famous for measuring the electron charge through the oil-drop experiment.

- He did not discover the neutron.