State the common characteristic of lanthanoids and actanoids which places them in the f-block of elements.

Explanation

To answer the question regarding the common characteristic of lanthanoids and actinoids that places them in the f-block of elements, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the f-block Elements**:
- The f-block elements consist of the lanthanoids and actinoids. These elements are characterized by the filling of f orbitals.

2. **Identifying the Last Electron Configuration**:
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