is Si2H6 polar or non polar?
The correct answer and explanation is:
Correct Answer:
Si₂H₆ (disilane) is a nonpolar molecule.
Explanation (300 words):
To determine whether Si₂H₆ (disilane) is polar or nonpolar, we must consider two main factors: bond polarity and molecular geometry (shape).
1. Bond Polarity:
Each Si–H bond is slightly polar because silicon (electronegativity ≈ 1.90) and hydrogen (electronegativity ≈ 2.20) have a small difference in electronegativity (about 0.3). Similarly, the Si–Si bond is nonpolar because it connects identical atoms. So while there are slightly polar bonds, the polarity is very small.
2. Molecular Geometry:
Si₂H₆ has a similar structure to ethane (C₂H₆). It consists of two silicon atoms bonded together (Si–Si) and each silicon atom is bonded to three hydrogen atoms in a tetrahedral arrangement.
This tetrahedral geometry around each Si atom ensures that the dipole moments of the Si–H bonds are symmetrically distributed in space. Due to this symmetry, the small dipoles in each Si–H bond cancel each other out.
3. Net Dipole Moment:
Although there are slightly polar bonds, the overall shape of Si₂H₆ is symmetric, which results in no net dipole moment. Therefore, the molecule as a whole is nonpolar.
4. Intermolecular Forces:
Because Si₂H₆ is nonpolar, its intermolecular forces are primarily London dispersion forces (a type of van der Waals force), which are relatively weak. This explains its low boiling point and why it’s a gas at room temperature.
Conclusion:
While Si₂H₆ contains slightly polar bonds, the overall molecule is nonpolar due to its symmetrical geometry and cancellation of bond dipoles. This is similar to how carbon dioxide (CO₂) is nonpolar despite having polar bonds.