On the basis of lanthanoid contraction, explain the following:
(i) Nature of bonding in `La_(2)O_(3)` and `Lu_(2)O_(3)`.
(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 lanthanoids oxides.

Explanation

(i) As the size decreases covalent character increases. Therefore, `La_(2)O_(3)` is more ionic and `Lu_(2)O_(3)` is more covalent.
(ii) As the size decreases from La to Lu, stability of oxo salts also decreases.
(iii) Stability of complexes increases as the size of lanthanoids decreases.
(iv) Radii of 4d and 5d-block elements will be almost same.
(v) Acidic character of oxides increasesf from La to Lu.