Section 2 review
The Bohr model for the hydrogen atom allowed electrons in atoms only to occupy particular, discrete orbits corresponding to quantized energy levels. Bohr could not explain why electrons favored these particular orbits; de Broglie proposed that the electron behaves like a wave at the atomic scale, so electron orbits correspond to circular standing waves or resonances. Quantized energy levels provide a direct explanation for absorption and emission of photons by atoms. Emission lines are produced by an atom when an electron makes a transition from a higher to a lower energy level. Absorption lines occur when the electron in an atom absorbs a photon with a specific energy, moving it from a lower to a higher energy level. An absorption-line spectrum appears when atoms absorb particular wavelengths of light from the spectrum of a background light source. Read the text aloud
phosphorescence, orbit, Bohr model, quantum number, quantized, energy levels, ground state, electron volt (eV), excited state, absorption, emission, scattering, spectral line, line spectrum, continuum spectrum, spectrograph, Pauli exclusion principle

Review problems and questions

  1. By using the Bohr model of the atom, should the size of the helium atom be larger or smaller than that of the hydrogen atom? Why? Read the text aloud Show
  1. One hydrogen atom has an electron in its n = 1 energy level, while another atom has an electron in its n = 2 level. Which one requires more energy to move the electron to the n = 3 level? To the n = ∞ level? Why? Read the text aloud Show
  1. What property of atoms produces an emission-line spectrum? Read the text aloud Show
  1. The hydrogen atom produces three distinct sets of spectral lines known as the Lyman, Balmer, and Paschen series.
    1. Describe the differences in the light emitted in these three series.
    2. Explain how these differences are related to the energy level transitions of the atom. Read the text aloud Show
  1. The electron in an atom changes energy levels, and in the process it emits a photon at a wavelength of 656.3 nm.
    1. Is the electron energy level higher before or after it emits the photon?
    2. In joules, what is the difference in energy between the two energy levels?
    3. What is this energy difference in electron volts? Read the text aloud Show
  1. An atom absorbs a photon of light that has a frequency of 1014 Hz.
    1. What is the energy of this photon of light?
    2. What is the energy difference between the energy level of the atom before it absorbs the photon and the energy level after it absorbs the photon?
    3. What part of the electromagnetic spectrum does this photon correspond to? Read the text aloud Show
  1. Two students were each trying to use the same type of spectrograph. One of them read in the instruction manual never to point the spectrograph at the Sun. The other student found instructions on the Internet for a spectrograph that said you could point it at the Sun. Which instructions should they follow? Why? Show

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