Why do actinoid elements show wide range of oxidation states ?

How do you prepare : (i) k_(2)MnO_(4) from MnO_(2) ? (ii) Na_(2)Cr_(2)O_(7) from NaCrO_(4) ? (b) Account for the following : (i) Mn^(2+) is more stable then Fe^(2+) towards oxidation to + 3 state. (ii) The enthelpy of atomization is lowest for Zn in 3d series of the transition elements. (iii) Actinoid elements show wide range of oxidation states.

(i) What are transition elements ? (ii) Why do transition elements show variable oxidation states ?

(a) Why do transition elements show variable oxidation states? (i) Name the element showing maximum number of oxidation states among the first series of transition metals from Sc (Z = 21) to Zn (Z = 30). (ii) Name the element which shows only + 3 oxidation state. (b) What is lanthanoid contraction? Name an important alloy which contains some of the lanthanoid metals.

Why do transition elements show variable oxidation state?

(a) Define transition elements. (b) Give general electronic configuration of f-block elements.(c ) Most of transition elements are coloured, why? (d ) Transition elements show variable oxidation states, why?

Give reasons for the following: (i) Transition metals exhibit a wide range of oxidation states. (ii) Cobalt (II) is very stable in aqueous solutions but gets easily oxidised in the presence of strong ligands. (iii) Actinoids exhibit a greater range of oxidation states than lanthanoids.