Hantaro Nagaoka - Saturnian Model of The Atom

Saturnian Model of The Atom

Physicists in 1900 had just begun to consider the structure of the atom. The recent discovery by J. J. Thomson of the negatively charged electron implied that a neutral atom must also contain an opposite positive charge. In 1903 Thomson had suggested that the atom was a sphere of uniform positive electrification, with electrons scattered through it like plums in a pudding, the plum pudding model.

Nagaoka rejected Thomson's model on the ground that opposite charges are impenetrable. He proposed an alternative model in which a positively charged center is surrounded by a number of revolving electrons, in the manner of Saturn and its rings.

In 1904, Nagaoka developed an early planetary model of the atom. Nagaoka's model was based around an analogy to the explanation of the stability of the Saturn rings (the rings are stable because the planet they orbit is very massive). The model made two predictions:

• a very massive nucleus (in analogy to a very massive planet)
• electrons revolving around the nucleus, bound by electrostatic forces (in analogy to the rings revolving around Saturn, bound by gravitational forces).

Both predictions were successfully confirmed by Rutherford (who mentions Nagaoka's model in his 1911 paper in which the nucleus is proposed). However, other details of the model were incorrect. In particular, charged rings would be unstable due to repulsive disruption, which is not the case with Saturn's rings, and Nagaoka himself abandoned it in 1908.

Ernest Rutherford and Niels Bohr presented the more viable Bohr model in 1913.