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The d-And-f-Block Elements
Question
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Which of the following cations are coloured in aqueous solutions and why?

 Sc3+, V3+, Ti4+, Mn2+ (Atomic number Sc = 21, V = 23, Ti = 22, Mn = 25)

Answer

The colour of cations is dependent on the number of unpaired electrons present in d-orbital. The electronic configuration of the following cations is as follows:

 Sc (Atomic number 21) = 3d1 4s2 and Sc3+ = 3d0 4s0. As d-orbital is empty, it is colourless.

 V (Atomic number 23) = 3d3 4s2 and V3+ = 3d2 4s0. As d-orbital is having 2 unpaired electrons, it undergoes d-d transition and shows green colour

 Ti = (Atomic number 22) = 3d2 4s2 and Ti4+ = 3d0 4s0. As d-orbital is empty, it is colourless

 Mn = (Atomic number 25) = 3d5 4s2 and Mn2+ = 3d5 4s0. As d-orbital is having 5 unpaired electrons, it shows pink color.

 

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

Why is the highest oxidation state of a metal exhibited in its oxide or fluoride only?

Which is a stronger reducing agent Cr2+ or Fe2+ and why?

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

Actinoid contraction is greater from element to element than lanthanoid contraction. Why?

On what ground can you say that scandium (Z = 21) is a transition element but zinc (Z = 30) is not?

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

Why the melting points of transition elements are high?

Why Zn, Cd and Hg are not regarded as transition elements?

Name the first element of 3rd transition series.