The `+3` oxidation states of langthanum `( Z= 57)`, gadolinium `(Z= 64)` and lutetium `(Z= 71)` are especially stable. Why ?

Explanation

To understand why the +3 oxidation states of lanthanum (La), gadolinium (Gd), and lutetium (Lu) are especially stable, we can analyze their electronic configurations and the stability associated with certain electron arrangements.

### Step-by-Step Solution:

1. **Determine the Atomic Numbers and Electronic Configurations**:
- **Lanthanum (La)**: Atomic number = 57
- Electronic configuration: [Xe] 5d¹ 6s²
- **Gadolinium (Gd)**: Atomic number = 64
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