Atom

Atomic Theory Timeline

  • 500 BCE

    Democritus

    Democritus
    Democritus was a student of a famous Greek Philosopher Leucippus. He first proposed the idea that all matter is composed of small indivisible particles. He believed that atoms of an element were different, but also the same. Also that substances have different characteristics from the atom's shape.
  • Christiaan Huygens

    Christiaan Huygens
    He created the wave theory of light. He believed that light was made up of waves and these waves vibrated in the way light traveled. His theory determined the true shape of saturn's rings, and also it's moon.
  • Isaac Newton

    Isaac Newton
    He studied gas and the possibility of atoms actually existing. He believed that they were small bits of mass that could be swimming everywhere, atoms and particles do move around.
  • John Dalton

    John Dalton
    Dalton's theory has greatly influenced the modern atomic theory of today. He said that all matter is composed of atoms, tiny, indivisible particles that cannot be created or destroyed. Atoms from different elements can combine to create compounds, and atoms change during chemical reactions.
  • Gustav Kirchhoff

    Gustav Kirchhoff
    He discovered 2 alkali metals with a device spectroscope. This discovery opened up a new way to find elements and to fill the holes that were missing.
  • James Maxwell

    James Maxwell
    He studied the connection between 2 forces which proved that electromagnetic waves are real. He conducted these experiments using the velocity of light and electromagnetic fields.
  • Heinrich Hertz

    Heinrich Hertz
    He was the first one to prove the existence of electromagnetic waves, based off of Maxwell's theory of light. He is most known for the discovery of electromagnetic radiation. Which refers to the waves of the electromagnetic field that carry radiant energy.
  • J.J Thomson

    J.J Thomson
    Thompson conducted the first experiments to determine the mass of an electron using the Cathode Ray Tube. He created his own visual of what an atom looks like, comparing it to plum pudding. He also said that atoms need to have a positively charged particle to neutralize negative charges from the electrons.
  • J.J Thomson's Plum Pudding Model

    J.J Thomson's Plum Pudding Model
  • Ernest Rutherford

    Ernest Rutherford
    Rutherford studied radiation and used gamma rays to conduct his experiments. He proved that the nucleus of the atom was positive by shooting alpha particles at a sheet of gold foil and watched which particles passed through, and which ones were deflected.
  • The Rutherford Model

    The Rutherford Model
    This model shows electrons orbiting the nucleus.
  • Albert Einstein

    Albert Einstein
    Albert Einstein created a formula to mathematically prove that atoms exist. This commonly heard formula is E=mc^2 and he also wrote a paper on Brownian Motion which helped strengthen the atomic theory.
  • Max Planck

    Max Planck
    He was the originator of the quantum theory. He has won many prizes for his theory and discoveries including the Nobel Prize in 1918. His theory reinvented the way humans understand atoms and subatomic particles.
  • Bohr Model

    Bohr Model
    In this model you can see the nucleus is in the centre of the atom while the electrons orbit around in their shells.
  • Neils Bohr

    Neils Bohr
    He theorized that the chemical properties and identity of the atom depended on the amount of electrons. He also introduced the idea that electrons can leap to and from different orbitals within the atom.