Who Discovered the Nucleus?

Ernest Rutherford, considered the father of nuclear physics, was given this title for his discovery of the nucleus. Rutherford put forth the first theoretical model of the nucleus, on which our modern theories of atomic structure are based. The significant discovery that the majority of an atom's mass can be found in one central region was achieved through testing we now refer to as "Rutherford's gold-foil experiment."

History

Born in 1871 in New Zealand Ernest Rutherford was educated as a scientist in both New Zealand and England. In 1908, six years after the completion of his graduate education Rutherford was awarded the Nobel Prize in Chemistry for his work on the nature of radioactivity. Rutherford proposed his theory of the nucleus while the physics chair at the University of Manchester.

Time Frame

Nearly a hundred years after the discovery of the atom by John Dalton the prevailing theory of atomic structure was the "plum pudding model." Developed by J.J. Thompson in 1904, the plum pudding model proposed that the electrons in an atom were placed proportionately throughout a positively charged field in an atom, the electrons like plums in a bowl of positively charged pudding. This model was the best current model for the structure of the atom at the time of Ernest Rutherford's experiments in 1911.

Features

During Rutherford's gold-foil experiment a series of helium particles were targeted at a sheet of gold foil only a few hundred atoms in thick. The path these helium particles took through the gold atoms allowed Rutherford and his associates to determine a new theory for the structure of the atom. The data from the experiment indicated that the mass of the gold atoms must be concentrated in one dense region and that most of the atom was made of empty space.

Significance

Rutherford's experiment disproved the current model of the atom, the plum-pudding model. Although Rutherford called the dense region he discovered "the central charge," we now understand it to be the atom's nucleus. Physicist Niels Bohr used Rutherford's discovery of the nucleus to refine the theoretical structure of the atom. Rutherford's discovery of the nucleus is the basis for current models of the atom and resulted in the foundation of a new field of science--nuclear physics.

Considerations

Scientists Hans Geiger and Ernest Marsden contributed greatly to the gold-foil experiments and the subsequent discovery of the nucleus. Rutherford, however, has been granted primary credit for the discovery, since the work was conducted under his instruction at the University of Manchester. As recognition for their important contributions the gold-foil experiment is also frequently called the Gieger-Marsden experiment.

Resources

• Read this Article in Spanish
• Detailed desription of the gold-foil experiment