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Transition and Inner Transition Elements — Chemistry STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceChemistryTransition and Inner Transition Elements3 Marks
Question
Why do the d-block elements form coloured compounds?
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Answer

  • Compounds (or ions) of many d-block elements or transition metals are coloured.
  • This is due to the presence of one or more unpaired electrons in (n – 1) d-orbital. The transition metals have incompletely filled (n – 1) cf-orbitals.
  • The energy required to promote one or more electrons within the d-orbitals involving d-d transitions is very low.
  • The energy changes for d-d transitions lie in visible region of electromagnetic radiation.
  • Therefore transition metal ions absorb the radiation in the visible region and appear coloured.
  • Colour of ions of d-block elements depends on the number of unpaired electrons in (n – 1) d-orbital. The ions having equal number of unpaired electrons have similar colour.
  • The colour of metal ions is complementary to the colour of the radiation absorbed.

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