Why is the separation of lanthanoid elements difficult?

(a) Separation of lanthanide elements is difficult. Explain. (b) Sm^(2+), Eu^(2+) and Yb^(2+) ions in solutions are good reducing agents but an aqueous solution of Ce^(4+) is a good oxidising agent. Why?

Discuss chemistry of lanthanoids.

Describe the factors on which the stability of an oxidation state of lanthanoid elements depends.

Why is the extraction of copper from pyrites more difficult than that from its oxide ore through reduction?

What are the characterstics of the transition elements and why are they called transition elements ? Which of the d-block elements may not be regarded as the transition elements ?

Explain why the enthalpy of formation and the entropy of formation of an element in its standard state at 298 K and 1 bar pressure are not equal ?

(i) What is the effect of lanthanoid contraction on the chemistry of the lanthanoids?

Why are most of the ions transition elements coloured?