Evolution of the Atom- Jillian McCann

Timeline created by jem0622
  • 450

    Democritus- Atomic Theory

    Democritus proposes that all matter is made up of indivisible particles called Atoms
  • Isaac Newton

    Newton suggested that atoms are held together with forces. He also stated that "matter is formed of solid, massy impenetrable particles”.
  • John Dalton

    Dalton created the atomic theory:
    1. all matter was composed of small indivisible particles called atoms
    2. atoms of a specific element have unique characteristics and weight
    3. there are three types of atoms: simple elements, compound (simple molecules), and complex molecules
  • William Crookes- Cathode Rays

    Crookes designed a tube where, virtually, no gas was present. The glow within the tube disappeared but one end of the tube was still glowing. An invisible ray was being emitted from the Cathode end called cathode rays
  • George Johnstone Stoney

    Introduced the term electron and estimated the charge to be that of a single hydrogen atom.
  • J.J.Thomson

    Thomson discovered that all atoms are made up of smaller particles. He originally called these particles 'corpuscles,' but they are now called electrons. This was determined when he studied Cathode Rays
  • Max Planck

    Planck explained that energy is not a continuous, flowing entity, but is carried in tiny, discontinuous units, which he named quanta. Each quantum's energy is equal to the frequency of radiation multiplied by the universal constant which Planck defined.
  • Hantoro Nagaoka

    He proposed a model in which a positively charged center is surrounded by a number of revolving electrons, in the manner of Saturn and its rings.The model made two predictions:
    -a very massive nucleus (similar to saturn)
    -electrons revolving around the nucleus, bound by electrostatic forces (similar to rings orbiting saturn)
  • Ernest Rutherford- Godl Foil Experiment

    He discovered the nucleus and developed a model of the atom. Electrons orbitted the central nucleus. He also discovered the proton through the Gold Foil Experiment. Not all paricles passed though the foil, some bounced back. Reasoning for positively charged particle:
    1. Repelled by similar charge so nucleus must be positively charged
    2. Few were deflected so it had to be smaller than an atom
    3. particles were travelling so fast that only something with a large mass could deflect
  • Robert Andrews Millikan

    He determined the charge carried by an electron, using the "falling-drop method"; he also proved that this quantity was a constant for all electrons.
  • Henry Moseley

    Moseley experimented with the x-ray spectra and discovered the relationship of the wavelength and atomic number. Before, atomic numbers had been thought of as a number based on sequence of atomic weights. Moseley predicted a number of missing elements and their periodic numbers in the Periodic Table as well
  • Niels Bohr- Quantum Theory

  • Werner Heisenberg- Uncertainty Principle

    It is not possible to know the definite position or velocity of a particle at quantum scales. "The quantum world is a world of statistics and probability, instead of exact certainty".
  • James Chadwick

    Chadwick discovered the neutron while originally working with Rutherford. When they were working together, they discovered that there was something else contributing to the atomic mass other than protons and electrons. Later on, Chadwick repeated experiments of other scientsist specifically looking for neutral particles with the same mass as a proton but with no charge
  • Electrons, Neutrons, Nucleus, and Protons, Definitions

    Electrons- a negatively charged particle; located in the electron cloud
    Neutron- A neutrally charged particle; located in the nucleus
    Nucleus- The center of the atoms containg neutrons and protons
    Protons- a positively charged particles; located in the nucleus
  • Law of Definite Prooportions Definition

    law stating that every pure substance always contains the same elements combined in the same proportions by weight
  • Law of Conservation of Mass definition

    law stating that every pure substance always contains the same elements combined in the same proportions by weight
  • Nuclear Model of Atom

    Nuclear Model of Atom
  • Spherical Model of Atom

    Spherical Model of Atom
  • Bohr Model of Atom

    Bohr Model of Atom
  • Plum Pudding Model

    Plum Pudding Model
  • Modified Nuclear Model of Atom

    Modified Nuclear Model of Atom
  • bibliography

    "Lab Aids." Lab Aids. N.p., n.d. Web. 5 Dec. 2013.
    "Explore PBS." PBS. PBS, n.d. Web. 05 Dec. 2013.
    Bio.com. A&E Networks Television, n.d. Web. 05 Dec. 2013.