Which of the following ion will give colourless aqueous solution ? (a) Ni²⁺ (b) Sc³⁺ (c) Cu²⁺ (d) Mn³⁺

Question 51 of 72

Q. Which of the following ion will give colourless aqueous solution ?

(a)

Ni^{2+}

(b)

Sc^{3+}

(c)

Cu^{2+}

(d)

Mn^{3+}

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Colour in transition-metal ions arises from d-d electronic transitions, which require partially-filled d-orbitals ( $d^1$ to $d^9$ ). An ion with $d^0$ (or $d^{10}$ ) configuration cannot undergo a d-d transition and is therefore colourless.

Scandium ( $Z=21$ ) has configuration $[Ar]3d^1 4s^2$ ; losing 3 electrons to form $Sc^{3+}$ removes both $4s$ electrons and the single $3d$ electron, leaving $[Ar]3d^0$ — no d-electrons at all, so $Sc^{3+}$ is colourless (this is why it is sometimes excluded from the 'true' transition series). $Ni^{2+}$ is $3d^8$ (green), $Cu^{2+}$ is $3d^9$ (blue), …

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Q.Which of the following ion will give colourless aqueous solution ?

Concept understanding — Position and Electronic Configuration of Transition Elements

Q.Which of the following ion will give colourless aqueous solution ?

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