Question

Write the colour of the following ions in aqueous solution: (i) Zn$^{2+$ (ii) Cu$^{2+}$ (iii) Fe$^{2+}$.}

Hint:

Colour in aqueous transition-metal ions arises from \(d\!\to d\) transitions; \(d^{10}\) ions like Zn$^{2+}$ are colourless, while Cu$^{2+}$ ( \(d^9\) ) is blue and Fe$^{2+}$ ( \(d^6\) ) appears pale green.

Answer 1

(i) Zn$^{2+}$ : colourless.
(ii) Cu$^{2+}$ : blue (azure/light blue).
(iii) Fe$^{2+}$ : pale green.