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The d-And-f-Block Elements
Question
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Which of the following ions will exhibit colour in aqueous solutions?

  • La3+ (Z = 57)

  • Ti3+ (Z = 22)

  • Lu3+

  • Sc3+

Answer

B.

Ti3+ (Z = 22)

Colour is obtained as a consequence of d-d (or f-f) transition, the presence of unpaired electrons is necessary conditions.
La3+ (Z = 57) = [Xe] 4f0 5d0 6s0 [ no unpaired electron]
Ti3+ (Z = 22) = [Ar] 3d1 4s0  [one unpaired electron]
Lu3+ (Z = 71) = [Xe] 4f14 5d0 6s0 [no unpaired electron]
Sc3+(Z = 21) = [Ar] 3d0 4s0 [no unpaired electron]
Hence, only Ti3+ will exhibit colour in aqueous solution.

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Some More Questions From The d-And-f-Block Elements Chapter

Explain why Cu+ ion is not stable in aqueous solutions?

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The outer electronic configuration of copper is 3d10 4s1, yet it is considered transition element. Why?

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Name the first element of 3rd transition series.

Though copper, silver and gold have completely filled sets of d-orbitals yet they are considered as transition metals. Why?

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