Atom Model Timeline

  • Atomic Model

    Atomic Model
    The atomic model was invented by John Dalton. He proposed his theory:-
    -The atoms are small and indivisible.
    -The atoms can't be created, divided and destroyed.
    -The atoms of the same elements have same properties whereas the atoms of the different elements have different properties.
    -Even the atoms of different elements can form compounds.
    -An element is identical.
  • Plum Pudding Model

    Plum Pudding Model
    -The plum pudding model was proposed by JJ Thompson soon after the discovery of an electron.
    -According to this model, the atom is a sphere of positive charge, and negatively charged electrons are embedded in it to balance the total positive charge.
    -The electrons are like plums in a pudding.
    -This added further depth to the first Atomic Model.
  • Nuclear Model

    Nuclear Model
    -Proposed by Ernest Rutherford
    -Atoms are mostly empty space
    -Most of the mass is concentrated in the center of the atom.
    This tiny, dense positively charged core is called the nucleus
    -Electrons are located outside the nucleus
    -He fired positively charged alpha particles at a thin sheet of gold foil. Most passed through with little deflection, but some deflected at large angles. This was only possible if the atom was mostly empty space with positive charge concentrated
  • Planetary Model

    Planetary Model
    -The planetary model was proposed by Niels Bohr.
    -Electrons orbit the nucleus in orbits that have specific size and energy and that the energy of the orbit is related to its size; the lowest energy is found in the smallest orbit.
    -When gaining energy, electrons move to farther orbit from the nucleus.
    -When losing energy, electrons move to closer orbit from the nucleus.
  • Quantum Mechanical Model

    Quantum Mechanical Model
    -The quantum model was proposed by Erwin Schrödinger.
    -Schrödinger stated that electrons don't move in set paths around the nucleus, but in waves. It is impossible to know the exact location of electrons; we have 'clouds of probability' called orbitals, in which we are more likely to find electrons.