Advertisements
Advertisements
Questions
Account for the following:
Cu+2 salts are coloured, while Zn2+ salts are white.
Zn2+ salts are white while Cu2+ salts are coloured. Why ?
Advertisements
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.
APPEARS IN
RELATED QUESTIONS
Which metal in the first transition series (3d series) exhibits + 1 oxidation state most frequently and why?
Out of Mn3+ and Cr3+, which is more paramagnetic and why ?
(Atomic nos. : Mn = 25, Cr = 24)
Calculate the ‘spin only’ magnetic moment of \[\ce{M^{2+}_{( aq)}}\] ion (Z = 27).
Which of the d-block elements may not be regarded as the transition elements?
Compare the general characteristics of the first series of the transition metals with those of the second and third series metals in the respective vertical columns. Give special emphasis on the following point:
Electronic configurations
Comment on the statement that elements of the first transition series possess many properties different from those of heavier transition elements.
Write balanced chemical equations for the conversion of `CrO_4^(2-)` to `Cr_2O_7^(2-)` in acidic medium and `Cr_2O_7^(2-)` to `CrO_4^(2-)`
in basic medium.
Explain why Zn2+ salts are white whereas Cu2+ salts are coloured.
Assertion: \[\ce{Cu^2+}\] iodide is not known.
Reason: \[\ce{Cu^2+}\] oxidises \[\ce{I^-}\] to iodine.
Consider the following standard electrode potentials (E° in volts) in aqueous solution:
| Element | M3+/M | M+/M |
| Al | - 1.66 | +0.55 |
| Tl | + 1.26 | -0.34 |
Based on these data, which of the following statements is correct?
