History of the Atomic Theory

History of the Atomic Theory

Mary FarrickerGrace Conti

470 B.C.

-Dalton's Model-proposed the existence of atoms-all elements are composed of atoms-atoms of the same element are exactly alike1803-described an atom as an invisible indestructible, solid sphere, like a billiar ballbecame one of the foundations of modern chemistryInteresting fact in 1803: The United States concluded the purchase of the Louisiana Purchase with France.

-Plum Pudding Model-theory of the negatively charged electron-proposed the isotope-atoms made from positively charged substance-cathode ray tube: passage of an electric current through gasgave off rays of negatively charged particles1904-atoms were made from a positively charged substance with negatively charged electrons scattered about Interesting fact in 1904: Russo-Japanese War began

-Bohr Model-electrons move in different orbits (energy levels) around the nucleus-energy levels located certain distances from the nucleus1913- placed each electron in a specific energy levelInteresting fact in 1913: Henry Ford creates first moving assembly line

-Gold Foil Experiment-atoms are mostly empty space-electrons circle the dense nucleus-nucleus contains positively charged particles-student of JJ Thomson1908- positively charged particles pass through the gold foil while other bounced away frrom the gold sheetInteresting fact in 1908: Messina Earthquake occured in Sicily, Italy.

-Democritus Model-matter cannot be broken down indefinately -once the smallest unit of matter is reached it is indivisible300 BC-"Atomos" - smallest piece of matterInteresting fact in 300 BC: The Temple of Zeus was beginning to be constructed

1766

1856

1871

1885

Democritus

John Dalton

JJ Thomson

Ernest Rutherford

Niels Bohr