Which ion would be expected to be colourless in aqueous solution?

  • A. Fe3+
  • B. Cu2+
  • C. Zn2+
  • D. Ni2+

Explanation

The zinc ion has a completely filled 3d10 configuration, so no d to d electronic transition is possible and no visible light is absorbed. Iron three, copper two and nickel two all have partly filled d subshells and give yellow brown, blue and green solutions respectively. Scandium three, being 3d0, is colourless for the complementary reason.

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