Which of the following B.P. order is not correct

Options

A. `SiF_(4) lt SiCl_(4)`
B. `CH_(4) lt SiH_(4) lt GeH_(4)`
C. `CH_(4) lt CF_(4)`
D. `He lt H_(2)`

Explanation

To determine which of the given boiling point (B.P.) orders is not correct, we will analyze each option based on the trends in boiling points in the periodic table.

### Step-by-Step Solution:

1. **Understanding Boiling Point Trends:**
- Boiling points generally increase down a group in the periodic table due to the increase in Van der Waals forces (dispersion forces) as the size of the atoms/molecules increases.
- Boiling points can also increase across a period due to increasing molecular weight and stronger intermolecular forces.

2. **Analyzing the Options:**
- **Option 1: SiF4 < SiCl4**
- Silicon (Si) is bonded to fluorine (F) and chlorine (Cl). As we move down the group from F to Cl, the boiling point increases due to the larger size and increased Van der Waals forces of Cl compared to F.
- This order is correct.

- **Option 2: CH4 < SiH4 < GeH4**
- Here, we are comparing methane (CH4), silane (SiH4), and germane (GeH4). As we move down the group from C to Si to Ge, the boiling point increases due to the increase in molecular size and Van der Waals forces.
- This order is also correct.

- **Option 3: CH4 < SiF4**
- In this case, we are comparing methane (CH4) with silane (SiF4). CH4 has weaker intermolecular forces compared to SiF4, which has strong dipole-dipole interactions due to the presence of highly electronegative fluorine atoms.
- Therefore, this order is correct as well.

- **Option 4: H2 < He**
- Hydrogen (H2) and helium (He) are being compared. Helium is a noble gas and has a higher boiling point than hydrogen due to its atomic structure and the stronger Van der Waals forces.
- The correct order is H2 < He, so this order is also correct.

3. **Identifying the Incorrect Order:**
- After analyzing all the options, we find that all the given orders are actually correct. However, the question asks for the order that is not correct. The order that stands out as potentially incorrect based on common knowledge is the comparison of CH4 and SiF4, as CH4 is expected to have a lower boiling point than SiF4 due to the strong intermolecular forces in SiF4.

### Conclusion:
The boiling point order that is not correct is **CH4 < SiF4**.