DaltonJohn Dalton FRS (6 September 1766 – 27July 1844) was anEnglish chemist , meteorologist and physicist .He is best known for his pioneering workin the development of modern atomictheory , and his research into color Dalton Modelblindness. First scientifically based atomic model, formulated by John Dalton The model was able to explain for the first time because the chemicals reacted in proportions fixed stoichiometries (Law of multiple proportions), and why when two substances react to form two or more different compounds, then the proportions of these relationships are integers.
ThomsonJoseph John "J. J." Thomson, OM FRS (18 December 1856 – 30August 1940) was a British physicist and Nobel laureate. He iscredited with discovering electrons and isotopes, and inventingthe mass spectrometer. Thomson was awarded the 1906 NobelPrize in Physics for the discovery of the electron and for hiswork on the conduction of electricity in gases. Thomson Model Proposed by Joseph John Thomson In this model, the atom is composed of negatively charged electrons in an atom positive, like a plum pudding. It was thought that the electrons are distributed uniformly around the atom. At other times, instead of a cloud of negative charge was running with a cloud of positive charge.
RutherfordErnest Rutherford, 1st Baron Rutherford ofNelson OM, FRS (30 August 1871 – 19 October1937) was a New Zealand-bornBritish chemist and physicist who became known asthe father of nuclear physics. He is considered thegreatest experimentalist since MichaelFaraday (1791–1867). Rutherford Model The Rutherford model or planetary model is a model of the atom devised by Ernest Rutherford. Rutherford directed the famous Geiger-Marsden experiment in 1909, which suggested, upon Rutherfords 1911 analysis, that the so-called "plum pudding model" of J. J. Thomson of the atom was incorrect. Rutherfords new model for the atom, based on the experimental results, contained the new features of a relatively high central charge concentrated into a very small volume in comparison to the rest of the atom and with this central volume also containing the bulk of the atomic mass of the atom. This region would be named the "nucleus" of the atom in later years.
BohrNiels Henrik David Bohr (7 October 1885 – 18November 1962Danish physicist who madefoundational contributions to understanding atomicstructure and quantum mechanics, for ) was a whichhe received the Nobel Prize in Physics in 1922. Bohr Model Bohr model explain the reason for the structureThis atomic model was introduced by Niels of the Rydberg formula, it also provided aBohr in 1913. justification for its empirical results in terms of-Describes the atom as a small, positively fundamental physical constants.charged nucleus surrounded by electrons that(The Rydberg formula is used in atomic physics totravel in circular orbits around the nucleus. describe the wavelengths of spectral lines of many chemical elements.)
ChadwickSir James Chadwick CH FRS (20 October 1891– 24 July 1974) was an English Nobellaureate in physics awarded for his discoveryof the neutron. Chadwick NeutronIt is remarkable that the neutron was not discovered until 1932 whenJames Chadwick used scattering data to calculate the mass of thisneutral particle. Since the time of Rutherford it had been knownthat the atomic mass number A of nuclei is a bit more than twice theatomic number Z for most atoms and that essentially all the massof the atom is concentrated in the relatively tiny nucleus.
Max Planck Max Karl Ernst Ludwig Planck, (April 23, 1858 – October 4, 1947) was a German theoretical physicist who originated quantum theory, which won him the Nobel Prize for Physics in 1918.Quantum TheoryQuantum theory is the theoretical basis of modern physics that explains the nature andbehavior of matter and energy on the atomic and subatomic level. In 1900, physicist Max Planckpresented his quantum theory to the German Physical Society. Planck had sought to discoverthe reason that radiation from a glowing body changes in color from red, to orange, and,finally, to blue as its temperature rises. He found that by making the assumption that energyexisted in individual units in the same way that matter does, rather than just as a constantelectromagnetic wave - as had been formerly assumed - and was therefore quantifiable, hecould find the answer to his question. The existence of these units became the first assumptionof quantum theory.