Mention the type of compounds formed when small atoms like H, C and N gettrapped inside the crystal lattice of transition metals. Also give physical and chemical characteristics of these compounds.

On the basis of Lanthanoid contraction, explain the following :

(i) Nature of bonding in La₂O₃ and Lu₂O₃.

(ii) Trends in the stability of oxo salts of lanthanoids from La to Lu.

(iii) Stability of the complexes of lanthanoids.

(iv) Radii of 4d and 5d block elements.

(v) Trends in acidic character of lanthanoid oxides.

(a) Answer the following questions :

(i) Which element of the first transition series has highest second ionization enthalpy?

(ii) Which element of the first transition series has highest third ionization enthalpy?

(iii) Which element of the first transition series has lowest enthalpy of atomisation?

(b) Identify the metal and justify your answer.

(i) Carbonyl M (CO)₅

(ii) MO₃F

(a) Transition metals can act as catalysts because these can change their oxidation state. How does Fe(III) catalyse the reaction between iodide and persulphate ions?

(b) Mention any three processes where transition metals act as catalysts.

A violet compound of manganese (A) decomposes on heating to liberate oxygen and compounds (B) and (C) of manganese are formed. Compound (C) reacts with KOH in the presence of potassium nitrate to give compound (B). On heating compound (C) with conc. H₂SO₄ and NaCl, chlorine gas is liberated and a compound (D) of manganese along with other products is formed. Identify compounds A to D and also explain the reactions involved.