The atomic theory

By mquintero123
  • 480 BCE

    Leucippus

    Leucippus
    He was the mentor of Democritus. Founder of the atomism. He stated that matter is homogeneous but consists of an infinity of small indivisible particles. These atoms are constantly in motion.
  • 460 BCE

    Democritus 460 - 370 BCE

    Democritus 460 - 370 BCE
    Adopted Leucippus theory, According to Democritus atoms were minuscule quantities of matter. He said that atoms cannot be destroyed, that they differ in size, shape and temperature, are always moving, and are invisible. He believed that there are an infinite number of atoms.

  • John Dalton (6 Sept, 1766 - 24 Jul, 1844)

    John Dalton (6 Sept, 1766 - 24 Jul, 1844)
    Dalton's atomic theory said that all matter was composed of atoms, inseparable building blocks in 1808. While all atoms of an element were identical, different elements had atoms of differing size and mass. Dalton theory was based on experiments, so that is why is called the truly scientific theory of the atom.

  • Eugene Goldstein (5 Sept, 1850 - 25 Dec, 1930)

    Eugene Goldstein (5 Sept, 1850 - 25 Dec, 1930)
    German physics that discovered protons and canal rays with a cathode ray experiment which knock electrons of atoms and attack them to a positive charge in 1886. With his work scientist could picture better the atom.

  • JJ Thompson (18 Dec, 1856 - 30 Aug, 1940)

    JJ Thompson (18 Dec, 1856 - 30 Aug, 1940)
    Discovered the electron in 1897. He proposed a model of the atom which he likened to plum pudding. The negative electrons represented the raisins in the pudding and the dough contained the positive charge. He won the Nobel prize.

  • Ernest Rutherford (30 Aug, 1871 - 19 Oct, 1937)

    Ernest Rutherford (30 Aug, 1871 - 19 Oct, 1937)
    He was a student of JJ Thompson, he also proved him wrong. Rutherford concluded that the atom consisted of a small, dense, positively charged nucleus in the center of the atom with negatively charged electrons surrounding it. The discovery of the nucleus is considered to be Rutherford's greatest scientific work in 1911.

  • Niels Bohr (7 Oct, 1885 - 18 Nov, 1962)

    Niels Bohr (7 Oct, 1885 - 18 Nov, 1962)
    Worked with JJ Thomson and Ernest Rutherford. Bohr model shows the atom as a small, positively charged nucleus surrounded by orbiting electrons in 1922. Bohr was the first to discover that electrons travel in separate orbits around the nucleus and that the number of electrons in the outer orbit determines the properties of an element, this was an explanation that underline the regularities of the periodic table. He won the Nobel price.

  • James Chadwick (20 Oct, 1891 - 24 Jul, 1974)

    James Chadwick (20 Oct, 1891 - 24 Jul, 1974)
    Discovered the neutron in 1932. Using evidence collected by Irene Joliot-Curie, who said that when beryllium was charged with positive alpha particles a streak was created. James Chadwick discovered that this streak was not caused by either electric or magnetic fields, they were neutral - neutrons. Neutrons were found to have the same mass as protons.