Atomic History Timeline

By MollyMMason
  • 400 BCE

    Democritus

    Democritus
    -Stated that all matter is made of atoms
    -Believed atoms are eternal and invisible
    -So small they cannot be divided
    -They fill up the space there are inhabiting completlty
    -Named them atoms from the greek word atomas which means "uncut"
    -The shape of the atom should correspond with the shape of the object it makes
    -He was a famous philosipher
    -Taught by Leucippus

  • John Dalton

    John Dalton
    -Atoms combine in different ways in different compounds
    -All matter is composed of tiny, indestructible, particles called atoms
    -Atoms are all alike and have the same atomic weight
    -All atoms of different elements have a mixed mass
    -Compounds contain atoms of different elements

  • J.J. Thompson

    J.J. Thompson
    -Discoverd electron
    -Developed "plum pudding" model of the atom
    -Won nobile prize in 1906
    -Used Cathode rays to test theory

  • Marie Curie

    -Discovered radium and polonium when investigating radioactive substances
    -First woman to win a nobel prize
    -First person and only woman to ever win 2 nobel prizes
    -Discovered 2 new elements with husband

  • E. Goldstein

    -Discovered protons
    -Used anode ray experiment to test theory
    -Atoms contain positively charged particles (protons)
    -He stated that in order to be electronically neutral there has to be positive particles to balance the negative ones

  • Robert Milikan

    -Found electric charge of atom
    -Oil drop experiment helped him discover this
    -Theory helped further understanding the structure of an atom and atomic theory

  • Ernest Rutherford

    Ernest Rutherford
    -Used gold-foil results to determine that all mass of mass are in a small positively charged ball located in the center of the atom
    -Discovered atoms contain a nucleus
    -Used high-powered alpha-particles with gold foil experiment to prove his theory

  • Quantum Mechanical Model (Wave Model)

    Quantum Mechanical Model (Wave Model)
    -Known as uncertainty principle
    -Quantum theory used complex shapes of norbits (electron clouds)
    -Volume of space likely to have electrons
    -All theories is still theory
    -Based upon quantum theory
    -Theory says it's impossible to know the exact position and movement of electrons

  • James Chadwick

    -Proved existence of neutron
    -Neutrons have no charge
    -Neutrons make up the nucleus with the protons
    -Found in nucleus with subatomic particles