# Problems for Chapter 6

6-1. Check the units of all of the equations in this section. Compute a 0 and E0.

6-2. Compute the orbital radius, velocity and energy of the first three levels of Hydrogen and Uranium. What general conclusions can you draw?

6-3. Using the results of the last section, compute the orbital radius, velocity and energy of the electrons in the outermost shell (ignore l , m and s) of Hydrogen and Uranium. Compare with your results for problem 6-1.

6-4. Group the elements in the Periodic Table by their n, l values.

6-5. Compute the bond energies in kJ / mol for the bonds in the table above.

6-6. Compute the wavelengths for Hydrogen atom transitions between all levels up to 7. Do not round until the end of your computations, since you may have very small numbers in denominators during the calculation.

6-7. When completely adapted to darkness, the human eye is able to detect a point light source if the power delivered to the retina is larger than 2 x 10 - 16 W. For a wavelength of 550 nm, how many photons must strike the retina each second to be detected?

6-8. 0.2 % of the solar radiation which reaches the surface of the earth lies in the 290 to 313 nm range, which causes sunburn. If the total radiation hitting the Earth's surface is 2100 J / cm 2 per 12 hours, and the burning efficiency is 50%, approximately how many photons caused the sunburn you received over 1 m 2 of your body by staying out in the sun for four hours?

6-9. It is often suggested that the full moon has an effect on the psychological condition of certain mammals. In fact, there does seem to be a correlation (although not necessarily a causal relationship) between the phase of the moon and the frequency of emergency room cases in hospitals. The moon is full when the earth is between the moon and the sun, and it is a "new" moon when it is between the sun and the earth. The average distance between the earth and the moon is 3.84 x 10 8 m. Note that the moon's perigee (distance of closest approach to the earth) varies with time, so that we need not concern ourselves with the variation of the earth-moon distance. The mass of the moon is 7.36 x 10 22 kg.

Compute the difference in the gravitational potential energy of electrons and molecules in your body (assume an average molecular weight of 14.77 for human tissue) between new and full moon (ignoring the earth). Refer to the table of radiation wavelengths and decide if you think there may be a causal relationship between phase of the moon and your mental state.

## Need more problems about atomic transitions?

If you have stumbled on this page, and the equations look funny (or you just want to know where you are!), see the College Physics for Students of Biology and Chemistry home page.

©1996, Kenneth R. Koehler. All Rights Reserved. This document may be freely reproduced provided that this copyright notice is included.

Please send comments or suggestions to the author.