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465 BCE
Democritus -Leucippus 465 BCE-360BC
leucippus an ancient greek philosopher ,that developed the atomic theory ,the mentor of Democritus that later adopt the atomic theory from his master ,and start saying that “The universe is composed of two elements: the atoms and the void in which they exist and move.” He said that All matter consists of invisible particles called atoms, that are indestructible solid but invisible. -
John Dalton ( 1766-1844)
He was a britan chemist, physicist, and meteorologist that put the atom as a solid idea and a fundamental chemical object ,he said that all elements are composed of atoms and he also said that a compound is composed of two or more different atoms and that a chemical reaction is the break of atoms .His escence today remain valid but he suffer of color blindness so he did achieve a lot of important discoveries and daltonism is called like that because john Dalton. -
Eugen Goldstein (1850-1930)
he discovered the canal rays which had electrical and magnetic properties opposite of an electron.that were positively charge protons and he also led the discovery of protons and that the cathode rays were not the only rays that will move in the opposite direction of the electrons because the Canal Rays do the same. -
Ernest Rutherford (1871-1937)
Ernest was British physics and know as the father of nuclear physics and a former student of J.J. Thomson on 1911 he proved that the plum pudding theory was incorrect ,he did a series of of experiments with alpha particles ,he discovered the the nucleus.Rutherford finally concluded that the atom consisted of a small, positively charged and dense nucleus in the center of the atom with negatively charged electrons surrounding it that is name the nucleus. -
Joseph John (J. J.) Thomson (1856-1940)
He proposed a interest model of the atom as a sphere of positive matter in where the electrons are positioned by electrostatic forces.He explained the a model of the atom like a plum pudding ,The negative electrons represented the raisins in the pudding and the cake have the positive charge ,He also discovered the electron by experimenting with cathode rays.The model of the atom did explain some of the electrical properties of the atom , but he failed in the experiment. -
Niels Bohr (1885-1962)
He was one of the most recognized scientists in the modern physics ,won a nobel prize for his structure of atoms.his greatest contribution to modern physics was the atomic model in which they shows the atom as a small, positively charged nucleus surrounded by orbiting electrons. he also discovered that the electrons travel in different and separate orbits. He also discovered that the number of electrons in the outer orbit determines the properties of an element. -
james Chadwick (1891-1974)
He discovered the neutron ,James Chadwick discoverd that this beam was not deflected by either electric or magnetic fields, meaning it contained neutral particles- neutrons. Neutrons were found to have the same mass as protons which accounted for more of the mass of the atom and allowed the masses. The common understanding of an atom was now a nucleus containing positively charged protons and neutral neutrons .
