History of the Atoms

By jasminesachdeva
  • 492 BCE

    Democritus

    Greek philosopher, Democritus, was among the first to suggest the existence of atoms. He believed that atoms were indivisible and indestructible.
  • 332 BCE

    Aristotle

    Aristotle concluded in his Metaphysics book that all things are made up of form and matter which can only be changed with growth, decay, or motion.

  • Dalton

    By using experimental methods, Dalton transformed Democritus' ideas on items into a scientific theory. Dalton studied the ratios in which elements combine in chemical reactions.

  • Rutherford

    New Zealand physicist, Ernest Rutherford, discovered that in the nuclear atom, the protons and neutrons are located in the nucleus. The electrons are distributed around the nucleus and occupy almost all the volume in the atom. He created the gold foil experiment to make these discoveries.

  • J.J. Thompson

    Thompson discovered isotopes as a result of sending ionized Neon through a magnetic and electric field. The mirrored image produced showed two different parabolas meaning there were tow different atomic masses.

  • Niehls Bohr

    Using Planck's Quantum Theory and Rutherford's study of the nucleus in atoms, Bohr came to the conclusion that atoms have a heavily charged nucleus with the electrons at a distance circling around it. This would later turn out to be the first accurate model of the atom.

  • Millikan and Chadwick

    Robert A. Millikan carried out experiments to find the quantity of charge carried by an electron. Millikan discovered the charge and mass of the electron is mass= 9.1x10^-28g. He used this and other info to conclude the mass of an electron is at least 1000x lighter than the lightest atom. James Chadwick, after finding an unnamed particle and discovering it's atomic mass Chadwick had discovered the neutron. Chadwick was awarded a Nobel Prize after his discovery.

  • De Broglie / Schrodinger

    Louis de Brogile determined that all forms of energy exist in both particles and wavelengths, establishing the wave-particle duality of nature. This ended the debate over particle vs wavelength that started with Planck. Based off of Louis de Brogile's work, Schrodinger(1926)came up with the quantum mechanical atomic model which shows the orbitals around the nucleus in constant motion, equidistant from each other and at different angles. This was made to describe the functions of waves.