Question

Which molecule is non planar as well as polar

• A. IF
• B. IF$_3$
• C. IF$_5$
• D. IF$_7$

Answer 1

Answer: (C)

IF$_5$

Answer 2

To determine which molecule is non-planar as well as polar, we need to analyze the molecular geometry and polarity of each given molecule using VSEPR theory.

1. IF:

   • Central atom: I. Valence electrons = 7.
   • Surrounding atom: F.
   • Steric number = (Valence electrons of I + Number of monovalent atoms) / 2 = (7 + 1) / 2 = 4.
   • Number of bond pairs = 1.
   • Number of lone pairs = Steric number - Number of bond pairs = 4 - 1 = 3.
   • Molecular geometry: AXE$_3$ corresponds to a Linear shape.
   • Planarity: A linear molecule is always planar.
   • Polarity: The I-F bond is polar due to the electronegativity difference between I and F. The molecule has a net dipole moment. Thus, IF is polar.
   • Conclusion: Planar and polar.

2. IF$_3$:

   • Central atom: I. Valence electrons = 7.
   • Surrounding atoms: 3 F.
   • Steric number = (7 + 3) / 2 = 5.
   • Number of bond pairs = 3.
   • Number of lone pairs = 5 - 3 = 2.
   • Molecular geometry: AX$_3$E$_2$ corresponds to a T-shaped geometry.
   • Planarity: A T-shaped molecule is planar.
   • Polarity: The I-F bonds are polar. The asymmetrical T-shape results in a net dipole moment. Thus, IF$_3$ is polar.
   • Conclusion: Planar and polar.

3. IF$_5$:

   • Central atom: I. Valence electrons = 7.
   • Surrounding atoms: 5 F.
   • Steric number = (7 + 5) / 2 = 6.
   • Number of bond pairs = 5.
   • Number of lone pairs = 6 - 5 = 1.
   • Molecular geometry: AX$_5$E corresponds to a Square pyramidal geometry.
   • Planarity: A square pyramidal molecule is non-planar. The central atom is out of the plane of the square base.
   • Polarity: The I-F bonds are polar. The asymmetrical square pyramidal geometry results in a net dipole moment. Thus, IF$_5$ is polar.
   • Conclusion: Non-planar and polar.

4. IF$_7$:

   • Central atom: I. Valence electrons = 7.
   • Surrounding atoms: 7 F.
   • Steric number = (7 + 7) / 2 = 7.
   • Number of bond pairs = 7.
   • Number of lone pairs = 7 - 7 = 0.
   • Molecular geometry: AX$_7$ corresponds to a Pentagonal bipyramidal geometry.
   • Planarity: A pentagonal bipyramidal molecule is non-planar (except for the plane containing the central atom and the five equatorial atoms).
   • Polarity: The I-F bonds are polar. However, the highly symmetrical pentagonal bipyramidal geometry results in cancellation of bond dipoles, leading to a net dipole moment of zero. Thus, IF$_7$ is nonpolar.
   • Conclusion: Non-planar and nonpolar.

Comparing the conclusions for each molecule, IF$_5$ is the molecule that is both non-planar and polar.