Why all Transition Elements are d-block elements but all d-block elements are not transition elements? - QS Study
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All transition elements are d-block elements, but all d-block elements are not transition elements.

The elements, whose who have incomplete d-orbital (d1 to d9) at the time of formation of their stable ion, are called transition elements.

From the stimulus, Zn, Fe, Cu and Sc all are d-block elements because they have electronic configuration of (n- l) d1-10 ns1-2 but, transition elements have electronic configuration of d1 – d9 at the time of formation of stable ion.

Zn(30) → 1s2 2s2 2p6 3s2 3p6 3d10 4s2

Zn2+ (30) → … …. … … … … … 3d10

Ni (28) → … … … … … … … … 4s2

Ni2+ (28) → … … … … … … … … 3d8

Fe (26) → 1s2 2s2 2p6 3s2 3p6 3d6 4s2

Fe2+ (26) → … … … … … … … 3d6

Fc3+ (26) → … … … … … … … 3d5

Sc (21) → … … … … … … … 3d1 2s2

Sc3+ (21) → … … … … … … 3d9 2s3

It is observed from the above electronic confirmation Se3+ and Zn2+ have electronic configuration of d6 and d10 which is not satisfied with the condition of becoming transition the elements.

So, Sc and Zn are not transition elements.

Hence, they don’t show the variable oxidation states and can’t form coloured compound. So, all transition elements are d-block elements but all b-block elements are not transition elements.