Why `B-X` bond distance in `BX_(3)` is shorter than theoretically expected value ?

Explanation

To understand why the `B-X` bond distance in `BX3` (where `X` is a halogen) is shorter than the theoretically expected value, we can break down the explanation into several steps:

### Step 1: Understanding the Electronic Configuration of Boron
- Boron has an atomic number of 5, and its ground state electronic configuration is `1s² 2s² 2p¹`. This means that in its outer shell, boron has three electrons (two in the `2s` subshell and one in the `2p` subshell).

### Step 2: Excitation of Electrons
- When boron forms `BX3`, it can promote one of its `2s` electrons to the `2p` orbital, resulting in an excited state configuration of `2s¹ 2p²`. This configuration allows boron to have three unpaired electrons available for bonding.

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