Which one of the following is the correct statement

Options

A. Berylliu7m exhibits coordination number of six
B. Chlorides of both beryllium and aluminium have bridged chloride structures in solid phase
C. `B_(2)H_(6).2NH_(3)` is known as 'inorganig benzene'
D. Boric acid is a protonic acid

Answer

To solve the question, we need to analyze each of the four statements provided and determine which one is correct.

### Step-by-Step Solution:

1. **Analyze Statement 1: "Beryllium exhibits a coordination number of 6."**
- Beryllium (Be) has an atomic number of 4, and its electronic configuration is 1s² 2s². Beryllium typically exhibits a coordination number of 4 in its compounds, particularly in beryllium chloride (BeCl₂), where it forms a tetrahedral structure. Therefore, this statement is **incorrect**.

2. **Analyze Statement 2: "The chlorides of both beryllium and aluminium have a solid-phase bridge-chloride structure."**
- Beryllium chloride (BeCl₂) and aluminium chloride (AlCl₃) both have structures that can be described as bridging chlorides in their solid forms. In the case of AlCl₃, it can form a dimer (Al₂Cl₆) in the solid state, where chlorine atoms bridge between aluminium atoms. Similarly, BeCl₂ can also exhibit a similar bridging structure. Therefore, this statement is **correct**.

3. **Analyze Statement 3: "B₂H₆.2NH₃ is known as inorganic benzene."**
- The compound known as inorganic benzene is actually B₃N₃H₆, not B₂H₆. Therefore, this statement is **incorrect**.

4. **Analyze Statement 4: "Boric acid is a protonic acid."**
- Boric acid (H₃BO₃) does not behave as a typical protonic acid; instead, it acts as a Lewis acid. It does not donate protons directly but can accept hydroxide ions. Thus, this statement is also **incorrect**.

### Conclusion:
The only correct statement among the four provided is **Statement 2**, which states that the chlorides of both beryllium and aluminium have a solid-phase bridge-chloride structure.

### Final Answer:
**The correct statement is: The chlorides of both beryllium and aluminium have a solid-phase bridge-chloride structure.**

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