Thomson's alleged “plum pudding”: A model that could never stand (yet persists in the minds and imagination of many physicists)

Thomson's atomic model is universally known as the “plum pudding” model, a somewhat metaphorical misnomer, given that the model actually envisioned electrons as being arranged in a precise geometric-dynamic structure. Through laborious calculations, this structure provided at least a qualitative framework for interpreting the periodic system of elements, atomic spectra, and beta radioactivity. Our study provides a survey --essentially a snapshot-- of how Thomson's atomic model is portrayed at various educational levels, from high school to PhD programs in physics. Our findings reveal that the model's name is almost universally taken literally by the vast majority of textbooks, teachers, and students, who describe it as consisting of a positively charged mass uniformly distributed, with electrons randomly arranged within it. Such a “plum pudding” model is clearly and fundamentally physically untenable. Thus, this is not merely a case of historical inaccuracy but rather a significant conceptual issue. Indeed, our analysis of conceptual problems associated with common textbook presentations of Thomson's model, along with the examination of its understanding in schools and universities, highlights a broader issue in teaching approaches that often fail to foster critical thinking, knowledge integration, and a genuine understanding of what is commonly called the Nature of Science.