History of the Atom and Matter

  • 460

    Democritus - 460 BC

    Democritus - 460 BC
    Greek philosopher, Democritus, develop the idea of atoms.
  • John Dalton - 1800's

    John Dalton - 1800's
    English chemist, John Dalton performed experiments with various chemicals that showed that matter, indeed, seem to consist of elementary lumpy particles (atoms).
  • Max Planck - 1900

    Max Planck - 1900
    Max Planck, a professor of theoretical physics in Berlin showed that when you vibrate atoms strong enough, such as when you heat an object until it glows, you can measure the energy only in discrete units. He called these energy packets, quanta.
  • Albert Einstein - 1905

    Albert Einstein - 1905
    Albert Einstein wrote a ground-breaking paper that explained that light absorption can release electrons from atoms, a phenomenon called the "photoelectric effect
  • Ernest Rutherfod - 1911

    Ernest Rutherfod - 1911
    Ernest Rutherfod thought that the electrons must exist somewhere within this empty space. Rutherford thought that the negative electrons orbited a positive center in a manner like the solar system where the planets orbit the sun.
  • Niels Bohr - 1912

    Niels Bohr - 1912
    Danish physicist, Niels Bohr came up with a theory that said the electrons do not spiral into the nucleus and came up with some rules for what does happen.
  • Ernest Rutherford

    Ernest Rutherford
    Rutherford identified the particles of the nucleus as discrete positive charges of matter. He found the protons mass at 1,836 times as great as the mass of the electron.
  • Paul Dirac - 1928

    Paul Dirac - 1928
    Paul Dirac produced equations which predicted an unthinkable thing at the time- a positive charged electron.
  • James Chadwick - 1932

    James Chadwick - 1932
    English physicist James Chadwick finally discover the neutron. He found it to measure slightly heavier than the proton with a mass of 1840 electrons and with no charge (neutral).
  • Werner Heisenberg - 1932

    Werner Heisenberg - 1932
    Werner Heisenberg concluded that charged particles bounce photons of light back and forth between them. This exchange of photons provides a way for the electromagnetic forces to act between the particles.
  • Carl Anderson - 1932

    Carl Anderson - 1932
    in experiments with cosmic rays, Carl Anderson discovered the anti-electron, which proved Paul Dirac's equations. Physicists call it the positron.