Which of the following molecule is planar?

Options

A. `CH_4`
B. `C_2H_4`
C. `NH_3`
D. `SiCl_4`

Answer

To determine which of the given molecules is planar, we will analyze the molecular geometry of each option provided:

1. **CH4 (Methane)**:
- Methane has a tetrahedral geometry due to the four hydrogen atoms bonded to the central carbon atom. The bond angles are approximately 109.5 degrees.
- **Conclusion**: CH4 is not planar.

2. **C2H2 (Acetylene)**:
- Acetylene has a linear structure due to the triple bond between the two carbon atoms. The bond angle is 180 degrees.
- **Conclusion**: C2H2 is not planar.

3. **C2H4 (Ethylene)**:
- Ethylene has a double bond between the two carbon atoms, resulting in a planar structure. The geometry around each carbon atom is trigonal planar, with bond angles of approximately 120 degrees.
- **Conclusion**: C2H4 is planar.

4. **NH3 (Ammonia)**:
- Ammonia has a trigonal pyramidal shape due to the presence of a lone pair on the nitrogen atom. The bond angles are approximately 107 degrees.
- **Conclusion**: NH3 is not planar.

5. **SiCl4 (Silicon Tetrachloride)**:
- Silicon tetrachloride has a tetrahedral geometry similar to methane, with bond angles of approximately 109.5 degrees.
- **Conclusion**: SiCl4 is not planar.

**Final Answer**: The planar molecule among the options is **C2H4 (Ethylene)**.