Abstract

The early years of the 20th century was a time when great strides were made in understanding the nature of atoms, which had been theretofore thought of as indivisible components of matter, with no internal structure. The laws of physics as they were then known were inadequate in accounting for a mounting number of mysteries, including: the periodicity of the known elements, the discrete character of atomic spectra, the origin of atomic radiation, and the large-angle scattering of radiation by matter. This talk will address the pre-eminent atomic models of that period, from J.J. Thomson’s inaptly named “plum pudding” model and Hantaro Nagaoka’s often-overlooked “Saturnian” model, both from 1904, to Ernest Rutherford’s 1911 proposal of the atomic nucleus, and the semi-classical model proposed by Niels Bohr in 1913. Through an analysis of the original publications, the merits and drawbacks of each model will be explored, and a qualitative and quantitative comparison of their theoretical predictions will be made with the available data of that time.