An accurate historical account of the development of ATOMIC PHYSICS
is probably the most hopeless task in the History of Science discipline.
The story began, almost certainly, before the dawn of recorded history.
Written records from Western antiquity date from as early as 450 BC,
when the Greek Leucippus proposed that all matter was composed of
s, i.e. miniscule indestructible subunits
of which there are only a few basic species. This view was picked up
by Leucippus' student, Democritos of Abdera, some 50 years later and
popularized by Epicurus of Samos around 300 BC, who developed the
"Atomist" philosophical system that was epitomized by the Roman
philosopher and poet Titus Lucretius Carus in about 60 BC.
Meanwhile, in 335 BC Aristotle countered with the proposition that matter was not grainy (as would seem to be required by the Atomist view) but smoothly continuous and composed of four basic ELEMENTS, also continuous: EARTH, AIR, FIRE and WATER. This picture gained popularity around 300 BC under Zeno of Cition, founder of the Stoics.
Thus the battle lines between a "bricks and mortar" view of matter and a "continuous" image of space, time and substance had been drawn well before the birth of Jesus; it took until the Twentieth Century to find the synthesis that allowed these two pictures (both of which, incidentally, are correct) to coexist in peace, though perhaps at the expense of what once passed for common sense.
Probably one key paradigm was Newton's CALCULUS, which taught everyone to understand CONTINUOUS mathematical behaviour in terms of DISCRETE "differentials" whose intervals were allowed to go to zero. Thus by the Ninteenth Century all scientists and mathematicians were intimately familiar with this trick for making the smooth look grainy and vice versa. The psychological stage was set for a new physical paradigm that reconciled Democritus' Atomism with Aristotle's Elements.
There was also an enormous amount of work done in the Middle Ages on determining exactly which ordinary household materials were true ELEMENTS and which were combinations of several elements - what we now call CHEMICAL COMPOUNDS. This was the work of untold numbers of ALCHEMISTS, most of whose work was done in secret for fear of persecution by those who considered such matters to be none of Humanity's business. Nevertheless, by the turn of the Nineteenth Century, a great many true ELEMENTS had been correctly identified and some regularities had begun to appear.
The next difficulty with the History of Atomic Physics is that a lot of it is Chemistry. Even after Alchemy became respectable under the new name of CHEMISTRY, a certain mutual disdain was cherished between Physicists and Chemists - which unfortunately lives on to this day - and consequently the History of Atomism reads a little differently in the Chemistry textbooks from the Physics version. Both are equally legitimate, of course, but since History is subject to politics and revisionism, one must always read any account with a certain healthy skepticism.
I will therefore make no claim that my account is fair, or even historically accurate; rather, my goal will be to show how the ideas might have developed in a perfectly logical sequence, using the powerful optics of hindsight. If you are stimulated by this "fake history" to go learn for yourself what really happened, then I will consider my goal achieved.