Draw the Lewis structure of carbon tetrafluoride (CF)

Draw the Lewis structure of carbon tetrafluoride (CF). Include all valence electrons. Name the electron geometry and molecular geometry for this molecule. The Electronegativity values are C – 2.5 and F 4.0. Determine if the bonds are polar and if the molecule is polar. Explain.

The Correct Answer and Explanation is :

Lewis Structure of Carbon Tetrafluoride (CF₄)

To draw the Lewis structure for carbon tetrafluoride (CF₄), follow these steps:

1. Determine the Total Number of Valence Electrons:

• Carbon (C) is in Group 14, so it has 4 valence electrons.
• Fluorine (F) is in Group 17, so each fluorine atom has 7 valence electrons. Since there are 4 fluorine atoms, the total number of electrons from fluorine is 7 × 4 = 28. Total valence electrons = 4 (from C) + 28 (from F) = 32 valence electrons.

1. Draw the Skeleton Structure:

• Carbon is the central atom, as it is less electronegative than fluorine. Connect the carbon atom to the four fluorine atoms with single bonds. Each single bond represents 2 electrons. This uses 8 electrons (4 single bonds × 2 electrons per bond).

1. Distribute the Remaining Electrons:

• After forming the bonds, we have 32 – 8 = 24 electrons left to distribute. Each fluorine atom needs 6 more electrons to complete its octet. These electrons are placed as lone pairs around each fluorine atom. Now, each fluorine atom has 3 lone pairs (6 electrons), and carbon is surrounded by 4 bonds, with no lone pairs.

1. Final Lewis Structure:

       F
       |
   F - C - F
       |
       F

Electron Geometry and Molecular Geometry:

• Electron Geometry: The electron geometry is determined by the number of bonding pairs and lone pairs around the central atom. In CF₄, there are 4 bonding pairs and no lone pairs on the carbon atom, making the electron geometry tetrahedral.
• Molecular Geometry: Since there are no lone pairs on the central atom and the bonding pairs are equally distributed, the molecular geometry is also tetrahedral.

Bond Polarity and Molecular Polarity:

• Bond Polarity: Fluorine is more electronegative than carbon, with an electronegativity difference of 1.5 (4.0 for fluorine and 2.5 for carbon). This creates a polar covalent bond between carbon and each fluorine atom, where the fluorine atoms have a partial negative charge (δ-) and the carbon atom has a partial positive charge (δ+).
• Molecular Polarity: Despite the polar bonds, the CF₄ molecule itself is nonpolar. This is because the molecule has a symmetrical tetrahedral geometry, and the dipoles from each C-F bond cancel each other out. The overall dipole moment of the molecule is zero, making CF₄ nonpolar.

Conclusion:

• Electron Geometry: Tetrahedral
• Molecular Geometry: Tetrahedral
• Bond Polarity: Polar C-F bonds
• Molecular Polarity: Nonpolar molecule

This is because the molecule’s symmetrical shape leads to the cancellation of the individual bond dipoles.