HWchapter28 - Chapter 28 Atomic Physics Quick Quizzes 1....

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Chapter 28 Atomic Physics Quick Quizzes 1. (b). The allowed energy levels in a one-electron atom may be expressed as ( ) 2 13.6 eV n EZ n =− 2 , where Z is the atomic number. Thus, the ground state ( ) 1 level n = in helium, with , is lower than the ground state in hydrogen, with . 2 Z = 1 Z = 2. (a). The energy of the photon emitted when the electron in a one-electron atom makes a transition from a state having principal quantum number to one having principal quantum number i n f n is () 2 22 11 eV fi nn γ    i n 13.6 Thus, for given values of and f n 2 , the energy of the photon emitted by a helium atom, with , is four times that of the photon emitted when an electron makes the corresponding transition in a hydrogen atom, with Z Z = 1 = . 3. (a) For n , there are 5 allowed values of A , namely A = 0, 1, 2, 3, and 4. 5 = (b) Since m A ranges from – A to + A in integer steps, the largest allowed value of A ( A = 4 in this case) permits the greatest range of values for m A . For 5 n = , there are 9 possible values for m A : -4, -3, -2, –1, 0, +1, +2, +3, and +4. (c) For each value of , there are A 2 1 + A possible values of . Thus, there is 1 distinct pair with A ; 3 distinct pairs possible with m A 0 = 1 = A ; 5 distinct pairs with ; 7 distinct pairs with ; and 9 distinct pairs with 2 = A 3 = A 4 = A . This yields a total of 25 distinct pairs of A and that are possible when m A 5 n = . 4. (d). Krypton has a closed configuration consisting of filled shells as well as filled 4 s and 4 p subshells. The filled =1, =2, and =3 n 3 n = shell (the next to outer shell in Krypton) has a total of 18 electrons, 2 in the 3 s subshell, 6 in the 3 p subshell and 10 in the 3 d subshell. 423
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424 CHAPTER 28 Answers to Even Numbered Conceptual Questions 2. Neon signs do not emit a continuous spectrum. They emit many discrete wavelengths as could be determined by observing the light from the sign through a spectrometer. However, they do not emit all wavelengths. The specific wavelengths and intensities account for the color of the sign. 4. An atom does not have to be ionized to emit light. For example, hydrogen emits light when a transition carries an electron from a higher state to the 2 n = state. 6. Classically, the electron can occupy any energy state. That is, all energies would be allowed. Therefore, if the electron obeyed classical mechanics, its spectrum, which originates from transitions between states, would be continuous rather than discrete. 8. The de Broglie wavelength of macroscopic objects such as a baseball moving with a typical speed such as 30 m/s is very small and impossible to measure. That is, hmv λ = , is a very small number for macroscopic objects. We are not able to observe diffraction effects because the wavelength is much smaller than any aperture through which the object could pass. 10. In both cases the answer is yes. Recall that the ionization energy of hydrogen is 13.6 eV.
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This note was uploaded on 06/07/2008 for the course PHYS 1C taught by Professor Smith during the Spring '07 term at UCSD.

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HWchapter28 - Chapter 28 Atomic Physics Quick Quizzes 1....

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