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Classification of Elements and Periodicity in Properties — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistryClassification of Elements and Periodicity in Properties5 Marks
Question
All transition elements are d-block elements, but all d-block elements are not transition elements. Explain.
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Answer

There are general characteristic properties of transition elements which can only exhibit if they have partially filled d-orbitals.
These properties are:
  1. Variable oxidation states: Due to relatively low reactivity of umpaired d-orbital electrons, transition elements can exihibit two or more oxidation states.
  2. Formation of coloured compounds: Due to partially filled d-orbitals they can undergo d-d electronic transitions which results into formation of coloured compounds.
  3. Paramagnetism: Due to unpaired d-orbital electrons, the compounds of transition metals are generally found paramagnetic.
But there are few d-block elements which have fully filled d-orbital for example zinc, cadmium and mercury which cannot exhibit these properties. Thus they are not considered as transition elements.

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