Matter is composed of small, solid, indivisible particles
called ATOMS. (Sometimes called the “billiard ball model”)
These particles always combined in whole number ratios and were therfore indivisible.
|1st periodic table arrangement in “grid” format. |
Arrangement was by WEIGHT.
Inventor of the SPECTROSCOPE. (see picture below)
Discovered Emmission or Bright – Line spectra.
Shown below: Continuous, Emission (bright-line), and Absorption (dark-line) types of spectra.
|Discovered the ELECTRON. |
Measured the RATIO of mass to charge in an electron.
Gold foil experiment. First to experiment on the structure of the atom.
A = Hard impenetrable center called the nucleus.
B = Atom is mostly empty space
C = Nucleus has a (+) charge, same as an alpha particle
|Added the concept of 7 ENERGY LEVELS to the Rutherford solar system model of the atom. Also explained Bright-line & absorbtion spectra by electrons changing energy levels.|
|German scientist to first show (mathematically) how light could exist in a particle format. Particle was called QUANTA (photon).|
|PHOTOELECTRIC EFFECT experiment. Early solar cell showing how light could act like a particle displacing electrons from an atom.|
|Uncertainity Principle. The exact position of an electron cannot be known all the time, due to the electron size and speed. Beginnings of the statistical model of the atom. Also was leader of the Nazi project to construct an atomic weapon during WWII.|
|Developed the statistical model of the atom to include areas of high electron probability called ORBITALS.|
|Exclusion principle (2 electrons maximum per orbital shape…) and the concept of electron spin.|
Hund’s Rule: Orbitals are created before they are filled…
Illustration of Hund’s Rule in 2p orbitals…
|“Pudding Cake” or “Raisin Bun” model of the atom. The atoms were solid, but had electrons embedded in them (like fruit in a fruit-cake).|
Modern arrangment of the modern Periodic table by Atomic number.
|Developed “electron dot” formula to illustrate valence electron positions in atoms, ions, and molecules.|