Development of Atomic Theory

Timeline created by waez666
  • 330

    Aristotle

    Aristotle
    He was the classical Greek philosopher that opposed the idea of an undivisible unit of matter. He believed that all matter consisted of four elements: Fire, Earth, Air and Water.
  • 450

    Democritus

    Democritus
    He was the Greek philosopher who proposed the first atomic theory: All matter is made of "atomos," and the properties of different elements depends of the shape of the atomos. Sweet food was made of round atomos, and bitter things such as wine were made of sharp atomos.
  • Benjamin Franklin

    Benjamin Franklin
    Franklin was fascinated by electricity and a great part of his life was spent exploring the dual nature of static electricity, in that objects can either be positively or negatively charged. Opposites attract and like charges repel.
  • Antoine Lavoisier

    Antoine Lavoisier
    He was the French chemist that is known today as the father of stoichiometry. He proposed the Law of Conservation of Mass in 1774.
  • John Dalton

    John Dalton
    Dalton hypothsized the first modern atomic theory in 1803:
    1. All matter consists of particles called atoms.
    2. Atoms of a given element are identical in size and shape.
    3. Atoms cannot be subdivided, created or destroyed.
    4. Atoms combine in simple whole number ratios to form compounds.
    5. In chemical reactions, atoms are combined, separated or rearranged.
  • Joseph Proust

    Joseph Proust
    He proposed the Law of Definite Proportions when he realized the mass ratio between sodium and chloride was always constant in any sample of salt.
  • Michael Faraday

    Michael Faraday
    He was the British experimentalist that discovered electrolysis and suggested that atoms were somehow related the electricity.
  • Dmitri Mendeleev

    Dmitri Mendeleev
    This Russian chemist is credited with creating the first periodic table. He suggested the octet rule in 1864 which catalyzed the worldwide urgency to understand the atom.
  • William Crookes

    William Crookes
    Crookes invented the frst Cathode ray which was later used by Joseph Thomson to discover the electron. Like Franklin, his passion was electricity but he never fulfilled his dream of discovering the negative source in matter.
  • Joseph Thomson

    Joseph Thomson
    After discovering the electron in 1892 using a cathode ray, Thomson propsed the firsrt atomic model that included both positive and negative particles. The "Plum Pudding" Model depicted a postively charged atom with negatively charged electrons embedded within the atom.
  • Henri Becquerel, Pierre and Mary Curie

    Henri Becquerel, Pierre and Mary Curie
    Becquerel is remembered in history as the first man to discover radioactivity in matter. Along with colleagues the Curies, they studied radioactive decay in many elements including Radium which they discovered.
  • Albert Einstein

    Albert Einstein
    In 1906, Einstein first suggested the idea of a photon. He studied quantic vibrations in liquids and concluded that there was indeed an atom. He significantly rejected the ideas of Heisenberg and the radicals during the earlier twenties.
  • Robert Milikan

    Robert Milikan
    Milikan calculated the mass and charge of a single electron in 1909 by means of the famous oil drop experiment. The charge was calculated to be 1.60217657 × 10-19 coulombs.
  • Ernest Rutherford

    Ernest Rutherford
    Rutherford performed the famous gold foil experiment in 1911 which redefined the nature of the atom. He proposed the planetary model of the atom which introduced a positive nucleus that is sorrounded by negative electrons.
  • Max Planck

    Max Planck
    A predecessor of Schrodinger, Planckn was among the conservative group that rejected the hypotheses of Heisenberg. He discovered and explained the nature of black-body radiation.
  • Niels Bohr

    Niels Bohr
    Bohr elaborated on the Planetary Model in 1922 by introducing the idea of quantum mechanics. He was the first to study the relationship between light, electrons, and energy.
  • Louis de Broglie

    Louis de Broglie
    Broglie goes down as the great compromiser who discovered the particle duality of quanta as both a wave and a particle.
  • Erwin Schrödinger

    Erwin Schrödinger
    A pioneer in quantum mechanics, Schrodinger produced the Schrodinger Euqation which shows the change in energy and orbitals during quantum jumps
  • Werner Heisenberg

    Werner Heisenberg
    Werner Heisenberg is the father of quantum mechanics and ended the decades long debate over atomic theory in 1927 when he proposed the UNcertainty Principle which states that either the velocity and location of an electron can be identified, but it is impossible to calculate both.
  • James Chadwick

    James Chadwick
    Chadwick closed the atomic debate by discovering the neutron in 1932. He was inspired by the works of Hiesenberg and continued his legacy.