1. 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

2. 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-

3. 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-

4. 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

5. 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

6. 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)

7. Bohr’s Atomic Radii for Hydrogen (Z=1) and Helium (Z=2)
n = 1, r = 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 = 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

8. 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