Arrange `BF_3, BCl_3, B Br_3, BI_3` in the decreasing order of Lewis acid character and explain.

Explanation

To arrange \( BF_3, BCl_3, BBr_3, \) and \( BI_3 \) in decreasing order of Lewis acid character, we need to analyze the electron deficiency of the boron atom in these compounds and how the size of the halogens affects the Lewis acidity.

### Step-by-Step Solution:

1. **Understanding Lewis Acids**:
- A Lewis acid is defined as a species that can accept an electron pair. In this case, boron halides are Lewis acids because boron is electron-deficient and can accept electrons to complete its octet.

2. **Electron Deficiency of Boron**:
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