CHAPTER 4 Electron Configurations Date __________ Rutherford to Bohr Flame tests lab… COLOR beginning to make connection between color and atomic structure… different colors…. __________________________________ Rutherford (Geiger, Marsden) model of the atom something different about structure

The Rutherford model of the atom e/m theory…. e/m radiation (light) consequence of : charged particles moving relative to each other the electron moves closer to the nucleus e/m PE decreases energy lost by e- has to “go” somewhere the e/m PE lost by the e- becomes a pure piece of energy Ephoton = h there is nothing around to transfer energy to e- transform (+) the nucleus (a photon) a photon is “born” this e- moves further, so… the amount of energy lost is greater so,… the photon that is “born” will have more energy than for e- Ephoton,2 > Ephoton,1 h2 > h1 different frequencies different colors e- e-

Rutherford’s model must be incomplete The Rutherford model of the atom e- in Rutherford’s model, the electrons can be anywhere so, can move any distance can lose any amount of energy the photons that are “born” can have any energy any frequency any color e- Rutherford’s model must be incomplete (+) the nucleus Rutherford’s model predicts all colors are emitted from an atom = white e- e- e-

Rutherford’s model of the atom is incomplete… everything is NOT _____________ we see things of _____________________ AND… (demo) not only are things different colors, see _________________from elements this evidence tells us… white different colors discrete colors

AND… (demo) not only are things different colors, see _________________from elements this evidence tells us ________________________________________ ________________________________ _________________________________ __________________________________ ___________________________________ discrete colors only certain colors… so, only certain frequencies so, only certain photon energies (Ephoton = h) so, only certain amounts of energy lost by electron so, electron can only move specific/certain distances the electrons can only be in certain places AND are in different places in atoms of different elements

Bohr’s Atomic Model electrons can only be in certain places in an atom Bohr modeled these places as circular orbits around the nucleus (like planets around the Sun) electrons can only be in and move between these orbits the question still remained, how does the atom not collapse… (quote)

Bohr’s Atomic Radii for Hydrogen (Z=1) and Helium (Z=2) n = 1, r = 0.521 Ǻ n = 2, r = 2.13 Ǻ n = 3, r = 4.78 Ǻ n = 4, r = 8.50 Ǻ n = 5, r = 13.3 Ǻ n = 6, r = 19.1 Ǻ n = 7, r = 26.0 Ǻ n = 1, r = 0.267 Ǻ n = 2, r = 1.06 Ǻ n = 3, r = 2.39 Ǻ n = 4, r = 4.25 Ǻ n = 5, r = 6.64 Ǻ n = 6, r = 9.50 Ǻ n = 7, r = 13.0 Ǻ . radii of Bohr’s orbits 0.52910-10 m

Photons are absorbed or emitted as electrons MOVE BETWEEN ORBITS the energy of the electron in the ath orbit is Ea the energy of the electron in the bth orbit is Eb - if the electron moves from the ath to the bth orbit it will lose potential energy equal to the difference between Ea and Eb - this energy will be transformed into a photon that is emitted from the atom ath e- e- h bth