Periodic Table Timeline

By loganho19
  • Period: 460 BCE to 370 BCE

    Democritus

    • Used term “Atomos” to describe the atom; the word meaning, “that which cannot be cut”
    • Defined the atom as the smallest unit of matter which still retains the identities and properties of that matter
  • Period: 384 BCE to 322 BCE

    Aristotle

    • Did not agree with Atomic Theory
    • Believed there were 4 elements; those being Fire, Earth, Water, and Air
  • Period: 300 BCE to 1500

    Alchemy

    • The primary form of flawed science to come out of Aristotle's refuting of Atomic Theory
    - The word 'Khemia' was used to describe the result of the fusion of the Greek idea of the 4 elements of nature and Egyptian religion (The word 'Alchemy' then came out of the word 'Khemia'). This science was further developed when the Arabs occupied Egypt in the 600s, and spread to Spain in the 700s
  • Period: 1500 to

    Alchemy

    • Division of Alchemists had taken place
    • One group focused on the discovery of new compounds, chemical reactions and chemical processes. This led to modern chemistry
    • This group invented a variety of things including distillation, percolation, extraction and rudimentary chromatography
    • The other group kept a continually focus on traditional alchemy and looked at the spiritual side of the science
  • Period: to

    Anton Laurent de La Voisier

    • Viewed as the Father of Modern Chemistry
    • Unlike previous alchemists, he relied on quantitative observations to develop conclusions
    • Proved oxygen causes combustion, disproving the Phlogiston Theory
    • Created the Law of Conservation of Mass, stating: Matter can change form, but cannot be created nor destroyed in a chemical reaction
    • Developed the Law of Conservation of Mass by proving that the mass of metal oxide is the same as the mass of the metal plus oxygen when the metal decomposes

  • Positive and Negative Charges

    Positive and Negative Charges
    • Benjamin Franklin discovers that electrical charges come in both the positive and negative varieties
    • He discovered that like charges repel, while opposite charges attract

  • Law of Definite Proportions/Law of Constant Composition

    • States: A chemical compund always contains exactly the same proportion of elements by mass.
    • Developed by Joseph Louis Proust
    • This statement was widely contradicted by chemists at the time, largely due to the fact that a difference between pure substances and mixtures had not been fully identified yet

  • Dalton's Atomic Theory

    Dalton's Atomic Theory
  • Period: to

    John Dalton

    • Considered the Father of Atomic Theory
    • His Atomic Theory of Matter States that:
      • Matter is made up of atoms that are indivisible and indestructable
      • All atoms of an element are identical (untrue)
      • Atoms of different elements have different weights and different chemical properties
      • Atoms of different elements combine in simple whole numbers to form compounds
      • Atoms cannot be created nor destroyed. When a compund decomposes, the atoms are recovered unchanged

  • William Crookes

    William Crookes
    • Crookes invented the Crookes Tube, which would go on to be turned into Cathode Ray Tubes in 1897 by Ferdinand Braun
      • These tubes have all air and matter removed and are coated with flourescent paint; when a battery is connected and the paint glows it means that there is radiation coming from the battery
    • Crookes placed a paddle wheel inside of one of these tubes, and when it spun, he concluded that cathode rays have mass

  • Sir John Joseph Thomson

    Sir John Joseph Thomson
    • Used charged plates to deflect a cathode ray
    • The ray was deflected away from the negative plate toward the positive plate
    • Thomson determined that the ray was made of negative particles
    • These negative particles were called electrons

  • Ernest Rutherford

    • Known as the Father of Nuclear
    • Discovered the radioactive half-life
    • Discovered Radon
    • Classified the types of radiation

  • Radioactivity

    • Antoine Henri Becquerel discovers radioactivity in Uranium ore
      • 'Becquerel' is now the unit of radioactivity
    • Marie and Pierre Curie discover and isolate polonium and radium from uranium ores
      • The study of radioactive elements got scientists thinking that there was something inside of the atom that gave it its identity, and if that thing changed the atom would transmute into another element

  • Gold Foil Experiment

    • Conducted in 1910 by Ernest Rutherford, Hans Geiger and Ernest Marsden
    • A sheet of gold foil was placed inside of a can that was coated in flourescent paint
    • A ray of alpha radiation was aimed at the sheet
    • It was anticipated that the paint behind the sheet would light up because the ray would travel through the foil
    • The anticipated result was obatained 99.9% of the time but in the other 0.1%, the other side of the can lit up
    • It was deduced that atoms were mostly empty space, with...

  • Robert Millikan

    Robert Millikan
    • Calculated the mass and charge of an electron
    • He spent years conducting experiments with a unique device
      • Drops of water or oil would be sprayed into a chamber that contained two magnetic plates
      • An x-ray would remove electrons from the molecules in the air
      • Droplets that hadn't captured one or more electrons would fall to the bottom of the chamber
      • Droplets that had captured electrons would be attracted to the positive plate and would either move up or fall slowly

  • Gold Foil Experiment

    Gold Foil Experiment
    • ... a positive charged center core that would have defelcted the ray a small percentage of the time

  • Neutron

    • After experimenting for a few years, James Chadwick discovers a third subatomic particle, the neutron, which has no charge
    • This dispproved Ernest Rutherford's theory that a third subatomic particle was a proton and electron bound together