The arrangement of ligands in order of their crystal field splitting energies is called _____ .

Explanation

The arrangement of ligands in order of their crystal field splitting energies is called the **spectrochemical series**.

### Step-by-Step Solution:

1. **Understanding Crystal Field Splitting Energy (CFSE)**:
- Crystal Field Splitting Energy refers to the energy difference between the split d-orbitals in a transition metal complex when ligands approach the metal ion. Different ligands cause different amounts of splitting.

2. **Identifying Ligands**:
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