1932

James Chadwick was born in Cheshire, England, on 20th October, 1891, the son of John Joseph Chadwick and Anne Mary Knowles. He attended Manchester High School prior to entering Manchester University in 1908; he graduated from the Honours School of Physics in 1911 and spent the next two years under Professor (later Lord) Rutherford in the Physical Laboratory in Manchester, where he worked on various radioactivity problems, gaining his M.Sc. degree in 1913. That same year he was awarded the 1851 Exhibition Scholarship and proceeded to Berlin to work in the Physikalisch Technische Reichsanstalt at Charlottenburg under Professor H. Geiger. 

Scientists today envision atoms as being composed of tiny, heavy, positively charged nuclei surrounded by clouds of extremely lightweight, negatively charged electrons. This model dates back to the 1920s, but it has its origin in ancient Greece. The philosopher Democritus proposed the existence of atoms around 400 B.C. No one really took up the idea with any fervor until English physicist John Dalton introduced his atomic theory in the early 1800s. Dalton's model was incomplete, but it persisted basically unchanged throughout most of the 19th century.

A flurry of research into the atomic model occurred at the end of the 19th and well into the 20th century, culminating in the Schrodinger model of the atom, which is known as the cloud model. Soon after physicist Erwin Schrodinger introduced it in 1926, James Chadwick – another English physicist – added a crucial piece to the picture. Chadwick is responsible for discovering the existence of the neutron, the neutral particle that shares the nucleus with the positively charged proton.

Chadwick's discovery forced a revision of the cloud model, and scientists sometimes refer to the revised version as the James Chadwick atomic model. The discovery earned Chadwick the 1935 Nobel Prize in physics, and it made possible the development of the atomic bomb. Chadwick participated in the super-secret Manhattan project, which culminated in the deployment of nuclear bombs on Hiroshima and Nagasaki. The bomb contributed to the surrender of Japan (many historians believe Japan would have surrendered anyway) and the end of World War II. Chadwick died in 1974.