Rise of the Quantum Atom

Abstract

Affirmation of the atom and the ever-deeper quests into the structure of the subatomic has been a central occupation of physics in the last hundred years. Penetration of the atom concept into our society's consciousness is so complete that most kids would recognize by sight miniature solar systems figures as atoms. Atomicity has a long history. However the physical structure of atoms could be meaningfully probed only after the discovery of X-rays by Roentgen.  This highly energetic and penetrating radiation provided the first direct probe into the subatomic. Concurrently, quantum ideas were developed to explain the workings of matter. In this article we analyze a scenario of this epochal era of modern physics, in particular a chain of events from the summer of 1912. These were outgrowths of Rontgen's discovery, namely, radioactivity, electrons and X-ray interference by crystals. Another was Rutherford's nuclear model of the atom and the theory of it. We explore the characters, technologies and related sequence of activities. Additionally in this article we attempt to answer the question - what "secret” inspired Bohr to withdraw from extant projects to get busy with the now famous atomic theory? Bohr's quantum theory of the atom was described in his trilogy of articles "On the constitution of atoms and molecules” which appeared in the Philosophical Magazine one hundred years ago in a rapid succession in 1913. It was truly revolutionary for Bohr to be so bold in 1913 to demand that the same quantum principles should apply to physics exactly the same way as to chemistry. Many of the pioneers including Bohr, were to be honored by numerous awards especially from the then new Nobel Prize. Culturally, the vision of electrons as tiny planets orbiting around a nucleus has become the signature icon of the nuclear age, which may be seen in most logos of atomic organizations including that of IAEA.