question_answer 55)

  The electronic configuration of gadolinium (Z = 64) is : (a) \[\left[ Xe \right]\text{ }4{{f}^{3}}5{{d}^{5}}\text{ }6{{s}^{2}}\]           (b) \[\left[ Xe \right]\text{ }4{{f}^{7}}5{{d}^{2}}6{{s}^{1}}\] (c) \[[Xe]4{{f}^{7}}5{{d}^{1}}6{{s}^{2}}\]               (d) \[[Xe]4{{f}^{8}}5{{d}^{6}}6{{s}^{2}}\]

Answer:

  (c) Gadolinium (64) is the seventh member of lanthanide series. Thus, it has 7 electrons on 4f-orbitals. General electronic configuration of lanthanide series is: \[[Xe]4{{f}^{1-14}}5{{d}^{1}}6{{s}^{2}}\] On this basis, the electronic configuration of gadolinium is:                 \[[Xe]4{{f}^{7}}5{{d}^{1}}6{{s}^{2}}\]