Explain the following facts:
Transition metals form coloured complexes.

Give reasons:
Among transition metals, the highest oxidation state is exhibited in oxoanions of a metal.

Give reasons:
Ce⁴⁺ is used as an oxidising agent in volumetric analysis.

Give reasons:
Zn²⁺ salts are white while Cu²⁺ salts are blue.

Why La, Gd and Lu has low value of 3rd ionisation enthalpies?

187. Given below are the electrode potential values, E° for some of the first row of transition elements:
Elements V(23) Cr(24) Mn(25)Fe(26)Co(27)Ni(28) Cu(29)
E°_M²⁺/M(V) –1.18 – 0.91 – 0.44 – 0.28 –0.28 –0.25 +0.34
Explain the irregularities in these values on the basis of electronic structures of atoms.

Complete the following reaction equations:
(i) Cr₂O₇ ² + Sn²⁺ + H⁺ →
(ii) MnO₄^– + Fe²⁺ + H⁺ →

Actinide cations are coloured? Why?