The History of Matter & Atoms

Timeline created by kelsmckeee
  • French chemist Antoine Lavoisier establishes the Law of Conservation of Mass

    States that mass is neither created nor destroyed in any ordinary chemical reaction.
  • French chemist Joseph-Louis Proust accumulates evidence for law of definite proportions

    French chemist Joseph-Louis Proust accumulates evidence for law of definite proportions
    Law of definite proportions states that every chemical compound contains fixed and constant proportions (by weight) of its constituent elements.
  • John Dalton proposed a theory with spherical atoms

    John Dalton proposed a theory with spherical atoms
    The spherical model in statistical mechanics is a model of ferromagnetism. John Dalton in 1803, proposed an "atomic theory" with spherical solid atoms based upon measurable properties of mass. Dalton's theory came after Democritus who theorized that all matter was made of invisibe particles called atoms. He was one of the creators of the first basis for the Atomic theory. The atomic theory states that all objects are made up of indestructible particles or atoms.
  • Rutherford names the proton

    Rutherford names the proton
    Eugene Goldstein along with Rutherford discovered the protons in cells. Ernest Rutherford proposed the name proton for the positively charges particles in the nucleus of an atom shortly after the end of World War 1.
  • J.J. Thomson conducts inovated cathode ray tube experiment

    J.J. Thomson constructed experiments to find a definitive and comprehensive answer about the nature of cathode rays. He showed that cathode rays were composed of a previously unknown negatively charged particle, and thus is credited with a discovery and identification of the electron.
  • Electron discovered by J.J. Thomson

    Electron discovered by J.J. Thomson
    An electron is a negatively charged subatomic particle, its symbol is e-.
  • Planck's Ideas forms bases of Quantum Theory

    The quantum theory in physics is based on the principle that matter and energy have the properties of both particles and waves, created to explain the radiation of energy from a blackbody.
  • Thomson discovers Plum Pudding Model

    Thomson discovers Plum Pudding Model
    J.J Thomson proposed this model in which the atom is composed of electrons surrounded by soup of positive charge to balance the electrons' negative charges, like raisins surrounded by pudding.
  • Gold Foil Experiment

    Hans Geiger and Ernest Marsden scatter alpha particles off a gold foil and observe large angles of scattering, suggesting that atoms have a small, dense, positively charged nucleus.
  • Nucleus discovered as a result of Ernest Rutherford's work

    Nucleus discovered as a result of Ernest Rutherford's work
    The nucleus is the very dense region consisting of protons and neutrons at the center of an atom.
  • Modified Nuclear Model

    Modified Nuclear Model
    Rutherford and Chadwick stated that it is protons and neutrons in the nucleus orbited by electrons in the electron cloud.
  • Bohr introduces Bohr Model

    Bohr introduces Bohr Model
    Niels Bohr depicts in his Bohr Model the atom as small, positively charged, nucleus surrounded by electrons that travel in circular orbits around the nucleus. He also said that the electrons can jump from one level to another.
  • Erwin Schrodinger discovers the Quantum Mechanical Model of the Atom

    Erwin Schrodinger discovers the Quantum Mechanical Model of the Atom
    The Quantum Mechanical Model is a model of atomic structure that is based on mathematics and can be used to explain observations made on complex atoms. He stated that the moving particles, electrons were similar to waves. He developed the model that illustrated that electrons are found with a blurry cloud called the electron cloud.
  • Exclusion principle

    Wolfgang Pauli formulates the exclusion principal for electrons in an atom
  • Heisenberg discovers the uncertainty principle

    Heisenberg discovers the uncertainty principle
    Werner Heisenberg discovered the uncertainty principle. The uncertainty principle is one of the most fundemental characteristics that distinguishes quantam mechanics from classical physics. He proposed that an electrons position and velocity can not be simultaneously known.
  • Chadwick proves neutrons exist

    Chadwick proves neutrons exist
    At the same time that Rutherford proposed the name proton for the positively charged particle, he proposed that the nucleus also contained a nuetral particle, eventually named the neutron. It was not until 1932 that James Chadwick was able to prove that these neutral particles exist, also known as neutrons.
  • J. Hans D. Jensen proposed the nuclear shell model

    The nuclear shell model is a model of the atomic nucleus which uses the Pauli exclusion principle to describe the structure of the nucleus in terms of energy levels.