Summary
emission and absorption spectrum
cathode rays are electrons; charge of an electron: 1.6 x 10-19 C
mass of the electron: 9.11 x 10-31 kg
cathode rays led to the discovery of X rays (electromagnetic waves)
Thomson’s atomic model: the “plum-pudding” model
Rutherford shows that the positive charge of an atom is concentrated in a very tinny place: the nucleus (100,000 times smaller than the atom)
Rutherford’s model “solar system” model of the atom
all objects emit electromagnetic radiation; characteristic spectral distribution curves; Wien and Stefan’s law
Planck’s theory about this heat radiation--> first clues that energies at the atomic level are quantized
The energy quanta: E= h f (h=6.63 X 10-34 Js, the Planck constant)
Electromagnetic waves (and light also) carries energy in quanta, called
photons. Energy of a photon with frequency f: E= h f
Einstein explains the photoelectric effect
Bohr’s model for the H atom incorporates Planck.s discrete energies and Einstein’s photons into the Rutherford’s model; it is based on three extra postulates
The Bohr model was succecsfull in accounting for many atomic observations, especially the emission and absorption spectra for hydrogen and ordering of the chemical elements