Atomic Model Timeline

  • 100

    Democritus Atomic Philosophy 492 BC

    Democritus Atomic Philosophy 492 BC
    Democritus was a Greek Philosopher. First to discover that everything was made up of atoms. he believed that atoms were indestructible.
  • Period: 100 to


  • John Dalton's theory

    John Dalton's theory
    Daltons transforms Democritus's ideas into a scientific theory. Dalton sess the atoms as tiny particles that has no internal structor. His model is a tiny solid sphere.
    Dalton's Atomic Theory:
    1)All matter is made of atoms. Atoms are indivisible and indestructible.
    2)All atoms of a given element are identical in mass and properties
    3)Compounds are formed by a combination of two or more different kinds of atoms.
    4)A chemical reaction is a rearrangement of atoms.
  • Cathrode Ray

    Cathrode Ray
    Discovered by British scientist William Crookes, cathrode rays are streams of electrons observed in vacuum tubes. He studied the green glow more and found that rays traveled through the cathrode and hit the ened of the tube, he called the rays "cathode rays",
  • J.J. Thomson Theory

    J.J. Thomson Theory
    J.J. Thomson was a British physicist. He discovered the existance of electrons in the atom. His discovery is later known as his "Plumpudding model." He pictures electrons embedded in a spere of a positive electrical charge.
  • Plumpudding theory

    Plumpudding theory
    J.J. Thompson proposed that atoms of electricity called electrons is surrounded by a soup of positive charge to balance the electrons' negative charges.
  • Hantaro Nagaoka

    Hantaro Nagaoka
    Nagaoka is a Japanese scientist. He stated that an atom has a cental nucleus with elelctrons moving around it, just like rings around saturn.
  • Ernest Rutherford Model

    Ernest Rutherford Model
    New Zealand scientist Ernest Rutherford finds that an atom has a small, dense positively charged nucleus. Electrons move around the nucleus. Most of the space is empty. His model failed to explain the chemical properties of elements. his model is known a the atomic model.
  • Niels Bohr

    Niels Bohr
    Bohr took Rutherford's model to the next level by describing how electrons circled the nucleus in fixed distances called orbitals.
  • Electron Cloud

    Electron Cloud
    Discovered by Erwin Schrödinger, Erwin built upon the thoughts of Bohr. He develops mathmatical equations to describe the motion of electrons in atoms. He also stated that rather than electrons being distributed within an electron configuration of shells and energy levels, they were arranged in orbitals which were systematically distributed
  • James Chadwick

    James Chadwick
    James discovered that the neutron has no charge. It is inside the atomic nuclei with protons.