10 September
Announcements
Chapter 7 problems: 2, 7, 9, 11, 13, 16, 20, 22, 23, 29, 31
ALEKS quizzes???
Exam next Wednesday (8/15)
7 – 9 pm
Rooms TBA but all in Clark
Through 7.2
Recitations next week
Tuesday – exam review, open to everyone
Thursday – go over the exam you will take on Wednesday
Revised model of the atom
Use the form on RamCT
Explain your concept of the atom
With words and pictures (do not cut and paste)
Talk about how it has changed from your initial model
Give reasons why things have changed
Where did new ideas come from?
If it hasn’t, talk about what is the same
Make a copy to study for the exam
Due the beginning of class Monday 9/13 or before
The photon
Einstein’s light ‘particle’
Bundles of electromagnetic energy
Connected to Planck’s quantum number
E = nhν “n” is not just a positive integer, but the number of photons being absorbed by the
atom
When n = 1, the equation calculates the energy of 1 photon
N = 2, energy of 2 photons
Planck’s formula can also be used to solve for the number of photons absorbed by an
atom
Calculating photons
If an atom absorbs 2.5 x 10 -16J of energy when light with a frequency of 1.51 x 10 Hz is 15
shone on it, how many photons were absorbed?
E = nhν → n = E / hν
-16 -34 15 -1
N = 2.5 x 10 J / (6.626 x 10 J*s x 1.51 x 10 s )
N = 2.5 x 10 -1J / 1.00 x 10 -1J
N = 249.9 → 250 (to 2 sig figs and a whole number)
The atom absorbed 250 photons of energy
Atomic spectra
Another key to understanding electrons in an atom
Line spectra – produced when an element is vaporized and energized, the light
produced is spread via a prism
Hydrogen spectrum
Line spectrum of hydrogen showed distinct s

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