Atomic Physics 1. Outline how the Bohr model of the hydrogen atom accounts for the spectrum of hydrogen (3)

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1 Name: Date: 1. This question is about models of the hydrogen atom. Atomic Physics 1 Outline how the Bohr model of the hydrogen atom accounts for the spectrum of hydrogen (3) The diagram below shows some of the energy levels of the hydrogen atom. E/eV n=4 n=3 n= n=1 (i) Outline, by reference to the diagram, what is meant by the term quantization of energy. Deduce that for the transition from the level n = 2 to the level n = 1, the wavelength of the photon emitted is m. 1

2 (iii) Suggest why the lines in the spectrum of atomic hydrogen become closer together as the wavelength of the emitted photons decreases. (c) Outline how the concept of matter waves leads to the Schrödinger model of the hydrogen atom (Total 12 marks) 2. This question is about the nuclear structure of the atom and atomic energy levels. When the electron was first discovered it led to the idea that an atom consists of a lump of positive charge in which the electrons are embedded. In 1912 Geiger and Marsden carried out an experiment to test the validity of this idea. The results of their experiment in fact suggested that the atom is mostly empty space with an electrically charged nucleus of relatively large mass occupying only a small amount of space. (This is the so-called nuclear model of the atom). Their experiment involved firing alpha particles at a thin sheet of gold foil. State the nature of an alpha particle.... 2

3 The diagram below shows a small part of the gold foil with two alpha particles A and B approaching the foil. A B gold foil (i) Some alpha particle trajectories lead to the idea that most of the atom is empty space. On the diagram, draw such a trajectory for the alpha particle A. Some other alpha particle trajectories lead to the idea that the atom has an electrically charged, relatively massive nucleus. On the diagram, draw such a trajectory for the alpha particle B. 3

4 (iii) Describe briefly how these trajectories lead to the idea of the nuclear model of the atom. In 1914 Niels Bohr suggested that the electrons in an hydrogen atom occupy discrete energy levels. The diagram below shows some of the principal energy levels. n = 8 n = 3 energy n = 2 n = 1 (c) (i) Label with the letter X, the energy level in which an electron will have zero potential energy. Explain how the line spectra of atomic hydrogen supports the idea of discrete energy levels. You may use the diagram above to support your answer. (Total 12 marks) 4

5 3. This question is about atomic spectra. An electron undergoes a transition from an atomic energy level of J to an energy level of J. Determine the wavelength of the emitted photon (Total 3 marks) 4. This question is about α-particle scattering. In 1913, Geiger and Marsden carried out an experiment in which α-particles were fired at a piece of gold foil. The diagram below shows two such α-particles A and B moving toward a gold nucleus in the directions shown. A nucleus B nucleus On the diagram above, draw possible paths followed by A and B. Explain how a knowledge of the initial KE of α-particles such as A enables an upper limit for the diameter of a nucleus to be estimated (3) (Total 5 marks) 5. This question is about models of the hydrogen atom. The Bohr model provides a partially successful explanation of the spectrum of the hydrogen atom. The model predicts that the energy, E, of the electron in the hydrogen atom is given by E = n 18 where n is an integer and E is in joules. 5

6 (i) By reference to this equation, describe how the Bohr model accounts for the line spectrum of the hydrogen atom. Calculate the shortest wavelength of light in the spectrum of atomic hydrogen. (iii) State one characteristic of the spectrum of atomic hydrogen which cannot be accounted for by the Bohr model. Outline by reference to position and momentum how the Schrödinger model of the hydrogen atom is consistent with the Heisenberg uncertainty principle (3) (Total 10 marks) 6

7 6. This question is about line spectra. Light is emitted from a gas discharge tube. Outline briefly how the visible line spectrum of this light may be obtained The table below gives information relating to three of the wavelengths in the line spectrum of atomic hydrogen. Wavelength / 10 9 m Photon energy / J Deduce that the photon energy for the wavelength of m is J (c) The diagram below shows two of the energy levels of the hydrogen atom, using data from the table above. An electron transition between these levels is also shown. (i) On the diagram above, construct the other energy level needed to produce the energy changes shown in the table above. Draw labelled arrows to represent the energy changes for the two other wavelengths shown in the table above. (Total 6 marks) 7

Topic 7 &13 Review Atomic, Nuclear, and Quantum Physics

Topic 7 &13 Review Atomic, Nuclear, and Quantum Physics Name: Date:. Isotopes provide evidence for the existence of A. protons. B. electrons. C. nuclei. Topic 7 &3 Review Atomic, Nuclear, and Quantum Physics D. neutrons.. The atomic line spectra of elements