Electrons orbit the nuclues at specific fixed radii similar to planets orbiting the sun. Electrons can jump to higher energy levels after absorbing specific amounts of energy. Likewise, electrons dropping from higher to lower energy levels will release certain amounts of energy in thr form of photons. Model was replaed with quantum mechanics.
Louis de Broglie
All matter has both particle and wave characteristics.
Elements are made up of unique atoms. Elements combine to make compounds. Compounds have constant ratios of atoms. Atoms are neither created nor destroyed in chemical reactions.
Photoelectric effect: When light with certain frequencies strikes a pieve of metal, it emits electrons form the emtal. Radiant energy behaves as a steam of tiny packets of energy (photons). Photons have properties of waves (wave-particle duality of nature).
Heisenberg Uncertainty Principle
It is not possible to know both the position and momentum of an electron at a particular moments. Electron orbitals are described in terms of probability.
Electrons will enter empty orbtials of equal energy when they are available.
Mawell provided a mathematical description of the general behavior of light. He described how energy in the form of radiation can travel through space as electric and magnetic fields.
Millikan calculated the charge of an electron.
Pauli Exclusion Principle
No two electrons in an atom have the same set of four quantum numbers.
Planck is the “father” of quantun mechanics. Energy can only be emitted or absorbed from atoms in fixed amounts.
Gold foil experiment: He shot a beam of alpha particles at a thin sheet of gold and found that the atoms in the foil must contain an extremely dense, positively charged core, sufficient to deflect the positively charged alpha particles. Atoms are mostly space. The nucleus is very dense positively charged center of atom. Electraons are small and travel around nucleus.
Through development of the Schrodinger equations, he was able to apply probability to describing the volume of spae of where an eletron would be located. Wave mechanics become the foundation for the development of the quantum model of the atom.
“Plum Pudding Model”: The Atom conststed of a positively charged, spherical mass with negatively charged electrons scattered throughout.