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

To answer the question based on the lanthanoid contraction, we will explore each part step by step.

### (i) Nature of bonding in `La_(2)O_(3)` and `Lu_(2)O_(3)`

1. **Understanding Ionic Size**: As we move from La to Lu, the ionic size decreases due to the lanthanoid contraction. This contraction occurs because of the poor shielding effect of the f-electrons.

2. **Bonding Character**: In `La_(2)O_(3)`, the larger La³⁺ ion has a greater ionic character, leading to predominantly ionic bonding. Conversely, in `Lu_(2)O_(3)`, the smaller Lu³⁺ ion has a higher charge density, which increases the covalent character of the bond.

...