Extra Credit: Unit 4 Lessons 17 and 18
Useful Formulas:
c = 3.0×108 m/s R = 2.18×10-18 J
h = 6.626×10-34 Jxs/(photon) n = energy levels
Open the accompanying activity from Ohio State University.
Go the pHET model at http://phet.colorado.edu/en/simulation/hydrogen-atom
Use the OSU instructions to complete this activity at least through the Bohr Model. Use this answer sheet to answer selected questions and as adjustments to the OSU activity.
Do the pHet activity Steps 1-18 fro the OSU sheet.
Questions:
1. If a photon of monochromatic light has a wavelength of 94 nm, what is its frequency, s-1?
2. What is the energy (J) of one photon?
3. What is the energy of one mol of photons at 94 nm?
Dalton: A brilliant model which is still useful but which was also wrong about an atom being non-divisible (smallest particle). However, it is still true that the atom is unique. I think the idea that the atom is the smallest particle that ‘retains all the characteristics of that element’ is still true. We now know that an atom consists of many smaller particles. In this class, we study the electrons, principally. Electrons are the particles involved in chemical reactions (“Valence” electrons). But, this is a very exciting time in physics. On March 14, 2013 the scientific community seemed to confirm the Higgs Boson particle – a/k/a/ as the ‘God particle”. See com/space/higgs-boson-confirmed-130314.htm”>http://news.discovery.com/space/higgs-boson-confirmed-130314.htm
Take a couple of minutes to look at this model.
Rutherford’s Classical Solar System: Be sure to slow this all the way down.
Question
4. Which of these is correct?: (Just highlight these in some way for me.)
A. There is a nucleus containing a proton.
B. There is an electron circling the nucleus, like a planet around a sun.
C. The electron looks like a wave.
D. The atom is not stable. The electron loses energy, spirals into the nucleus, and the atom is destroyed.
Comment: What does this mean to our model? It means that the electron must have its own ‘ground-state’ energy that resists/prevents the destruction of the atom.
Bohr Model:
Questions:
5. What happens when the photons hit the electron?
6. Is Energy increased or decreased when the electron and photon collide?
7. Does anything happen in the Emission Spectrum when the photon hits?
8. What happens IN THE EMISSION Spectrum when the photon returns to ground-state?
Do a couple of the exercise at 16-19.
Questions:
In Number 13:
9. Calculate (SHOW ME): Use transition from n = 2 to n = 3 at 655 nm
a. The frequency of the wavelength
b. The Energy of the wavelength using Plank’s Constant
c. The Energy of the transition
d. The predicted wavelength using Rydberg’s equation.
#10. : Identify the relationship between the Principal Quantum Number (n) and the energy level of the Bohr Model.
Follow-Up questions:
11. How long did you spend on this lab?
12. The purpose is to understand how ONE electron acts. Unfortunately, Bohr’s model falls apart for anything except the very simplest possible relationship. Nevertheless, I think it is a good tool to ‘see’ these foundational concepts. WHAT DO YOU THINK? Please write a few short sentences to tell me how you feel about the activity and whether you would recommend a similar activity as a future lab.
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