Consider the hydrides of group 14 elements
1. `CH_4`
2. `SiH_4`
3. `GeH_4`
4.`SnH_4`
The correct sequence of thermal stability is

Options

A. `1 lt 2 lt 3 lt 4`
B. `1 lt 2 lt 4 lt 3`
C. `1 gt 2 gt 3 gt 4`
D. `1 gt 2 gt 4 gt 3`

Answer

To determine the correct sequence of thermal stability for the hydrides of group 14 elements (CH₄, SiH₄, GeH₄, SnH₄), we can analyze the factors affecting their thermal stability.

### Step-by-Step Solution:

1. **Identify the Hydrides**: The hydrides of group 14 elements are:
- CH₄ (Methane)
- SiH₄ (Silane)
- GeH₄ (Germane)
- SnH₄ (Stannane)

2. **Understand the Trend in Group 14**: As we move down the group from carbon to tin, the size of the atoms increases due to the addition of electron shells. This increase in atomic size affects the bond characteristics.

3. **Analyze Bond Length and Strength**:
- The bond length between the central atom (C, Si, Ge, Sn) and hydrogen increases as we move down the group.
- For example, the bond length of C-H is shorter than that of Si-H, which is shorter than Ge-H, and so on.
- Longer bond lengths generally lead to weaker bonds.

4. **Relate Bond Strength to Thermal Stability**:
- Weaker bonds are less stable and can break more easily when subjected to heat, leading to lower thermal stability.
- Therefore, as we move down the group, the thermal stability of the hydrides decreases.

5. **Establish the Order of Thermal Stability**:
- Since CH₄ has the strongest bond and thus the highest thermal stability, followed by SiH₄, GeH₄, and finally SnH₄ with the weakest bond, the correct order of thermal stability is:
- CH₄ > SiH₄ > GeH₄ > SnH₄

### Final Answer:
The correct sequence of thermal stability is:
**CH₄ > SiH₄ > GeH₄ > SnH₄**