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AP Chemistry: Unit 7: Atomic Spectra & Quantum Numbers: Homework
1. Consider the following types of electromagnetic radiation:
(1) microwave
(2) ultraviolet (3) radio waves
(4) infrared
(5) x-ray
(6) visible
a. Arrange them in order of increasing wavelength.
b. Arrange them in order of increasing frequency.
c. Arrange them in order of increasing energy.
2. Portions of electromagnetic waves A, B, and C are represented below (not drawn to scale):
A
B
C
Rank them in order of (a) increasing frequency; (b) increasing energy; (c) increasing amplitude.
(d) If wave B just barely fails to cause a current when shining on a metal, is wave A or C more
likely to do so? (e) If wave B represents visible radiation, is wave A or C more likely to be IR
radiation?
3. A radio wave has a frequency of 3.6 • 1010 Hz. What is the energy in Joules of one photon of this
radiation?
4. An FM station broadcasts classical music at 93.5 MHz (megahertz, or 106 Hz). Find the wavelength
(in m, nm, and Å) of these radio waves.
5. Rank the photons in terms of increasing energy: (a) blue (λ = 453 nm); (b) red (λ = 660 nm); (c)
yellow (λ = 595 nm)
6. Cobalt-60 is a radioactive isotope used to treat cancers of the brain and other tissues. A gamma ray
emitted by an atom of this isotope has an energy of 1.33 MeV (million electron volts; 1 eV
(1.602 X 10-19 J). What is the frequency (in Hz) and the wavelength (in m) of this gamma ray?
7. (a) The first step in the formation of ozone in the upper atmosphere occurs when oxygen
molecules absorb UV radiation of wavelengths ≤242 nm. Calculate the frequency and energy of
the least energetic photons.
(b) Ozone absorbs light having wavelengths of 2200 to 2900 Å, thus protecting organisms on
Earth’s surface form this high energy UV radiation. What are the frequency and energy of the
most energetic of these photons?
8. Arrange the following H atom electron transitions in order of increasing frequency of the photon
absorbed or admitted: (a) n = 2 to n = 4; (b) n = 2 to n = 1; (c) n = 2 to n = 5; (d) n = 4 to n = 3.
9. Give all the possible m1 values for orbitals that have each of the following: (a) l = 2; (b) n = 1;
(c) n = 6, l = 3
10. Are the following quantum number combinations allowed? If not, show 2 ways to correct them.
a. n = 1, l = 0, m1 = -1
b. n = 4, l = 3, m1 = -1
c. n = 3; l = 1, m1 = 0
11. The maximum number of electrons in a shell with the principle quantum number equal to 4 is:
a. 2
b. 10
c. 16
d. 32
12. Determine the frequencies of electromagnetic radiation of the following wavelengths:
a. 0.10 nm
b. 5000 Å
c. 4.4 μm
d. 89 m
e. 562 nm
13. Which of these electron transitions correspond to absorption energy and which to emission?
a. n = 2 to n = 4
b. n = 3 to n = 1
c. n = 5 to n -= 2
d. n = 3 to n = 4
14. What feature of an orbital is related to each of these quantum numbers:
a. principal quantum number (n);
b. angular momentum quantum number (1);
c. magnetic quantum number (m1)?
15. Are the following quantum number combinations allowed? If not, show two ways to correct them:
a. n = 2, l = 0, m = -1
b. n = 4, l = 3, m = -1
c. n = 7, l = 1, m = 0
d. n = 3, l = 2, m = 3
16. The photoelectric effect is illustrated in a plot of the kinetic energies of electrons ejected from the
surface of potassium metal or silver metal at different frequencies of incident light.
Kinetic
energy
a.
b.
c.
d.
frequency 
Why don't the lines begin at the origin?
Why don't the lines begin at the same point?
From which metal will light of a shorter wavelength eject an electron?
Why are the slopes of the lines equal?
17. A metal ion M/1+ has a single electron. The highest energy line in its emission spectrum occurs
at a frequency of 2.961 X 1016 Hz. Identify the ion.
18. As space exploration increases, means of communication with humans and probes on other
planets are being developed. (a) How much time (in s) does it take for a radio wave of frequency
8.93 X107 s -1 to reach Mars, which is 8.1 X 107 km from Earth? (b) If it takes this radiation 1.2 s to
reach the Moon, how far (in m) is the Moon from Earth?
19. Enormous numbers of microwave photons are needed to warm macroscopic samples of
matter. A portion of soup containing 252 g of water is heated in a microwave oven from 20.°C to
98°C, with radiation of wavelength 1.55 X10-2 m. How many photons are absorbed by the water in
the soup?
20. In a typical fireworks device, the heat of the reaction between a strong oxidizing agent, such as
KC1O4, and an organic compound excites certain salts, which emit specific colors. Strontium salts
have an intense emission at 641 nm, and barium salts one at 493 nm. (a) What colors do these
emissions produce? (b) What is the energy (in kJ) of these emissions for 5.00 g each of the
chloride salts of Sr and Ba? (Assume that all the released is converted to light emitted.)
21. Fish-liver oil is a good source of vitamin A, which is measured spectrophotometrically at a
wavelength of 329 nm.
a. Suggest a reason for using this wavelength.
b. In what region of the spectrum does this wavelength lie?
c. When 0.1232 g of fish-liver oil is dissolved in 500. mL of solvent, the absorbance is 0.724
units. When 1.67 X 10-3 g of vitamin A is dissolved in 250. mL of solvent, the absorbance is
1.018 units. Calculate the vitamin A concentration in the fish-liver oil.
22. Electric power is typically given in units of watts (1 W = 1 J/s). About 95% of the power output
of an incandescent bulb is converted to heat and 5% to light. If 10% of that light shines on your
chemistry text, how many photons per second shine on the book from a 75-W bulb? (Assume the
photons have a wavelength of 550 nm.)