Which of the following statement is `//` are true ?

Options

A. Based on VSEPR theory, the number of 90 degree `F-Br` angles in `BrF_(5)` is four.
B. Molecular geometries of both `(CH_(3))_(3)N` and `(SiH_(3))_(3)N` are trigonal planar.
C. The `C-C` bond length in `C_(2)` is larger than `O-O` bond length `O_(2)`.
D. For ozone molecule, one oxygen `-` oxygen bond is stronger than the other oxygen `-` oxygen bond.

Explanation

To determine which of the statements regarding the chemical bonding in the given compounds are true, we will analyze each statement step by step.

### Step 1: Analyze the first statement about BRF5
- **Statement**: The number of 90-degree F-Br angles in BRF5 is 4.
- **Analysis**:
- The hybridization of bromine in BRF5 can be calculated using the formula:
\[ H = \frac{1}{2} \left( \text{Valence electrons of Br} + \text{Number of monovalent atoms} - \text{Charge} \right) \]
- Bromine has 7 valence electrons, and there are 5 fluorine atoms (monovalent), so:
\[ H = \frac{1}{2} (7 + 5 - 0) = \frac{12}{2} = 6 \quad \Rightarrow \quad \text{Hybridization} = sp^3d^2 \]
- This indicates that there are 6 hybrid orbitals. Since there is one lone pair, the geometry is octahedral with the lone pair at the axial position.
- The bond angles are affected by the lone pair, and thus none of the F-Br angles are 90 degrees; they are reduced to about 84 degrees due to lone pair-bond pair repulsion.
- **Conclusion**: This statement is **false**.

### Step 2: Analyze the second statement about trimethylamine and trisilane
- **Statement**: The molecular geometry of trimethylamine and trisilane are trigonal planar.
- **Analysis**:
- Trimethylamine (N(CH₃)₃) has a nitrogen atom with one lone pair and three methyl groups. Its geometry is trigonal pyramidal, not trigonal planar.
- Trisilane (Si₃N) does exhibit trigonal planar geometry due to back bonding between the lone pair of nitrogen and the d-orbitals of silicon.
- **Conclusion**: This statement is **false** because trimethylamine is not trigonal planar.

### Step 3: Analyze the third statement about bond lengths
- **Statement**: The carbon-carbon bond length in C2 is larger than the oxygen-oxygen bond length.
- **Analysis**:
- In C2, the carbon atoms are connected by a double bond (C=C), while in O2, the oxygen atoms are also connected by a double bond (O=O).
- However, oxygen is more electronegative than carbon, which pulls the electron density closer to the oxygen atoms, resulting in a shorter bond length.
- **Conclusion**: This statement is **true**.

### Step 4: Analyze the fourth statement about ozone
- **Statement**: For ozone, one O-O bond is stronger than the other.
- **Analysis**:
- Ozone (O₃) exhibits resonance, meaning that the two O-O bonds are equivalent due to the delocalization of electrons.
- Therefore, it is incorrect to say that one bond is stronger than the other; both bonds are equivalent in strength.
- **Conclusion**: This statement is **false**.

### Final Conclusion
After analyzing all statements, we find that only the third statement is true.

### Summary of True Statements
- Only the third statement: "The carbon-carbon bond length in C2 is larger than the oxygen-oxygen bond length" is true.