Scientists and their contributions for the atomic structure
Aristotle
Aristotle disbelieved the ancient Greek theory of atoms being of different sizes, regular geometric shapes and beig in constant motion. He didn't think atoms could be in constant motion in a void. He developed the theroy that all matter consisted of four elements: Earth, Air, Water and Fire. There were also four qualities: dryness, hotness, coldness, and moistness. Fire was dry and hot, water was moist and cold, etc. Each of these elements move naturally in a line to their "proper place," where it will be at rest. Aristotle's theory also had two forces: conflict and harmony. Conflict was thought to cause bad things, and harmony good things. Aristotle also believed that the heavens were made of a fifth, superior element named aither. Aristotle's theory was used for almost 2000 years, until after the scientific revolution, when other theories prevailed
-https://ph.answers.yahoo.com/question/index?qid=20090225050600AAAHwgJ
Empedocles
Empedocles' philosophy is best known for being the originator of the cosmogenic theory of the four Classical elements. He also proposed powers called Love and Strife which would act as forces to bring about the mixture and separation of the elements. These physical speculations were part of a history of the universe which also dealt with the origin and development of life. Influenced by the Pythagoreans, he supported the doctrine of reincarnation
-http://en.wikipedia.org/wiki/Empedocles
Democritus
Democritus was an influential Ancient Greek pre-Socratic philosopher primarily remembered today for his formulation of an atomic theory of the universe.The theory of Democritus and Leucippus held that everything is composed of "atoms", which are physically, but not geometrically, indivisible; that between atoms, there lies empty space; that atoms are indestructible; have always been, and always will be, in motion; that there are an infinite number of atoms, and kinds of atoms, which differ in shape, and size. Of the mass of atoms, Democritus said "The more any indivisible exceeds, the heavier it is." But his exact position on weight of atoms is disputed.
-http://en.wikipedia.org/wiki/Democritus
Lavoisier
Lavoisier was known for his experimentation skills. One of his favorite experiments being turing HgO into Hg+O. He used this experiment to help himself come up with the Law of Conservation. The law states that matter cannot be made or destroyed. He also hints at the rearrangement of matter in reactions. Matter rearranged, but never disappeared.He began the conversation on what an atom was exactly.
-http://historyoftheatomictheory.weebly.com/antoine-lavoisier.html
John Dalton
Democritus first suggested the existence of the atom but it took almost two millennia before the atom was placed on a solid foothold as a fundamental chemical object by John Dalton (1766-1844). Although two centuries old, Dalton's atomic theory remains valid in modern chemical thought.
-http://www.iun.edu/~cpanhd/C101webnotes/composition/dalton.html
Jj Thomson
His atomic theory identified that electrons inside an atom could show, meaning that atoms were not invisible. Thomson suggested that the model of an atom as a sphere of positively charged matter with negatively charged electrons surrounding them. He stated that electrons were positioned by electrostatic forces. J.J. Thomson had started to discover atomic theory that gives complete explanation of atomic structure.
-http://wiki.answers.com/Q/What_was_JJ_Thomson's_major_contributions_to_the_atomic_theory
Ernest Rutherford
He publishes his atomic theory describing the atom as having a central positive nucleus surrounded by negative orbiting electrons. This model suggested that most of the mass of the atom was contained in the small nucleus, and that the rest of the atom was mostly empty space. Rutherford came to this conclusion following the results of his famous gold foil experiment. This experiment involved the firing of radioactive particles through minutely thin metal foils (notably gold) and detecting them using screens coated with zinc sulfide (a scintillator). Rutherford found that although the vast majority of particles passed straight through the foil approximately 1 in 8000 were deflected leading him to his theory that most of the atom was made up of 'empty space'.
-http://www.rsc.org/chemsoc/timeline/pages/1911.html
Neil Bohr
Bohr developed the Bohr model of the atom, in which he proposed that energy levels of electrons are discrete, and that the electrons revolve in stable orbits around the atomic nucleus, but can jump from one energy level (or orbit) to another. Although the Bohr model has been supplanted by other models, its underlying principles remain valid. He conceived the principle of complementarity: that items could be separately analysed in terms of contradictory properties, like behaving as a wave or a stream of particles. The notion of complementarity dominated Bohr's thinking in both science and philosophy.
-http://en.wikipedia.org/wiki/Niels_Bohr
James Chadwick
Chadwick made a fundamental discovery in the doorman of nuclear science.
He proved the existence of neutrons.James predicted the atom would have a neutron. He established that atomic number is determined by the numbers of protons in an atom. He also discovered the fourth subatomic particle,the neutron.
-https://ph.answers.yahoo.com/question/index?qid=20091101155422AAbz1h6