John Dalton (1808) Atomic Theory:
According to Dalton, things are made up of small particles called atoms. Atoms cannot be created, destroyed or divided. Each element has its own identified atoms.
J. J. Thomson (1897) The Discovery of Electrons
http://www.chemheritage.org/discover/chemistry-in-history/themes/atomic-and-nuclear-structure/thomson.aspx
J.J Thomson found out electrons by his cathode-ray experiment. According to Thomson, atoms are divisible as it has much smaller negatively-charged particles inside known as electrons.
E. Goldstein (1900) The Discovery of Protons
http://www.xtimeline.com/evt/view.aspx?id=372419
E. Goldstein found protons by anode-ray experiment. Goldstein stated that since atom contains negatively-charged particles called electrons, there need to be positively-charged particles known as protons to make it neutrals.
E. Rutherford (1911) The Discovery of Nucleus
http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1908/rutherford-bio.html
E. Rutherford make his alpha particle scattering experiment to provide basic modern atomic structure. As he stated, atom consists of two part: nucleus and extra nuclear part. He proved that atom has a large empty space and has a heavy positively charged at the centre called nucleus.
James Chadwick (1932) The Discovery of Neutrons
Chadwick showed that atom contains neutral-charged particles in the nucleus known as neutrons along with electrons and protons.
N. Bohr (1940) Modern Concept of Atomic Model
http://www.nndb.com/people/895/000099598/
According to Bohr, atom is composed of nucleus which contains neutrons and protons inside it with the electrons that moving around different imaginary paths called orbits or shell.
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