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Account for the following: Cu+2 salts are coloured, while Zn+2 salts are white. - CBSE (Science) Class 12 - Chemistry

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Account for the following:

Cu+2 salts are coloured, while Zn+2 salts are white.

Zn2+ salts are white while Cu2+ salts are coloured. Why ?

Solution 1

Zn2+ salts have a completely filled set of d-orbitals (3d10), while Cu2+ has an incompletely filled set of d-orbitals (3d9), and therefore, d–d transition is possible in Cu2+, leading to blue colour.

Solution 2

Element/Ion Electronic Configuration
Zn 3d10 4s2
Zn2+ 3d10
Cu 3d10 4s1
Cu2+ 3d9

The colours of salts of transition metals are due to the d-d transition that depend on the presence of incompletely filled d-orbitals. Zn2+ has completely filled d-orbitals (3d10), while Cu2+ has incompletely filled d-orbitals (3d9); therefore, d-d transition is possible in Cu2+, which imparts colour to copper(II) salts.

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Solution Account for the following: Cu+2 salts are coloured, while Zn+2 salts are white. Concept: General Properties of the Transition Elements (D-block).
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