In which of the following molecule/ion all the bonds are not equal?

Options

A. `XeF_(4)`
B. `BF_(4)^(-)`
C. `C_(2)H_(4)`
D. `SiF_(4)`

Explanation

To determine which molecule or ion has unequal bond lengths, we can analyze the given options one by one.

### Step-by-Step Solution:

1. **Identify the Molecules/Ions:**
The options given are XCF4, SF4, C2H4, and SiF4.

2. **Analyze XCF4 (Xenon Tetrafluoride):**
- **Valence Electrons Calculation:**
- Xenon (Xe) has 8 valence electrons.
- Each fluorine (F) has 1 valence electron, and there are 4 fluorines: 4 × 1 = 4.
- Total = 8 + 4 = 12 valence electrons.
- **Hybridization:**
- The hybridization is determined to be sp³d² (6 electron pairs: 4 bond pairs and 2 lone pairs).
- **Molecular Geometry:**
- The shape is square planar.
- All bond lengths are equal in this configuration.
- **Conclusion:** All bonds are equal in XCF4.

3. **Analyze SF4 (Sulfur Tetrafluoride):**
- **Valence Electrons Calculation:**
- Sulfur (S) has 6 valence electrons.
- Each fluorine has 1 valence electron, and there are 4 fluorines: 4 × 1 = 4.
- Total = 6 + 4 = 10 valence electrons.
- **Hybridization:**
- The hybridization is sp³d (5 electron pairs: 4 bond pairs and 1 lone pair).
- **Molecular Geometry:**
- The shape is see-saw.
- The presence of a lone pair leads to unequal bond lengths.
- **Conclusion:** Not all bonds are equal in SF4.

4. **Analyze C2H4 (Ethylene):**
- **Structure:**
- Ethylene has a double bond between the two carbon atoms and single bonds to hydrogen atoms.
- **Bond Types:**
- The presence of a double bond (C=C) and single bonds (C-H) leads to different bond lengths.
- **Conclusion:** Not all bonds are equal in C2H4.

5. **Analyze SiF4 (Silicon Tetrafluoride):**
- **Valence Electrons Calculation:**
- Silicon (Si) has 4 valence electrons.
- Each fluorine has 1 valence electron, and there are 4 fluorines: 4 × 1 = 4.
- Total = 4 + 4 = 8 valence electrons.
- **Hybridization:**
- The hybridization is sp³ (4 bond pairs and 0 lone pairs).
- **Molecular Geometry:**
- The shape is tetrahedral.
- All bond lengths are equal in this configuration.
- **Conclusion:** All bonds are equal in SiF4.

6. **Final Conclusion:**
- The molecules where not all bonds are equal are C2H4 and SF4. However, since the question asks for a single option, the most distinct case is C2H4 due to the presence of a double bond.

### Answer:
The molecule in which all the bonds are not equal is **C2H4**.