Draw the Lewis structure for the SF4 and SF₆ molecules and determine if each molecule is polar or nonpolar.

Draw the Lewis structure for the SF4 and SF₆ molecules and determine if each molecule is polar or nonpolar.

The Correct answer and Explanation is:

Lewis Structures of SF₄ and SF₆

SF₄ (Sulfur Tetrafluoride):

1. Step 1: Count valence electrons.

• Sulfur (S) has 6 valence electrons.
• Fluorine (F) has 7 valence electrons. There are 4 fluorine atoms, so 4 × 7 = 28 electrons from fluorine.
• Total valence electrons = 6 + 28 = 34.

1. Step 2: Place sulfur in the center and attach four fluorine atoms around it.

• Each sulfur-fluorine (S-F) bond contains 2 electrons, so 4 bonds use up 8 electrons (4 × 2 = 8).

1. Step 3: Distribute the remaining electrons.

• 34 total valence electrons minus 8 (for bonds) leaves 26 electrons. These are placed as lone pairs on the fluorine atoms (6 electrons on each fluorine).

1. Step 4: Complete the sulfur’s octet.

• Sulfur can have more than 8 electrons due to its expanded octet capability. There are 2 remaining electrons, which form a lone pair on sulfur. The structure is see-saw shaped with 4 bonds and 1 lone pair.

SF₆ (Sulfur Hexafluoride):

1. Step 1: Count valence electrons.

• Sulfur has 6 valence electrons.
• Fluorine has 7 valence electrons. There are 6 fluorine atoms, so 6 × 7 = 42 electrons from fluorine.
• Total valence electrons = 6 + 42 = 48.

1. Step 2: Place sulfur in the center and attach six fluorine atoms around it.

• Each sulfur-fluorine bond uses 2 electrons, so 6 bonds use 12 electrons.

1. Step 3: Distribute the remaining electrons.

• 48 total valence electrons minus 12 (for bonds) leaves 36 electrons, distributed as lone pairs on the fluorine atoms (6 electrons on each fluorine). The structure is octahedral with 6 bonds and no lone pairs on sulfur.

Polarity of SF₄ and SF₆

• SF₄ is polar. Its asymmetrical see-saw shape causes an uneven distribution of charge. The lone pair on sulfur causes a dipole moment, making SF₄ polar.
• SF₆ is nonpolar. It has a symmetrical octahedral shape. Even though sulfur forms polar S-F bonds, the symmetry cancels out the dipole moments, making the molecule nonpolar.

Conclusion:

• SF₄ is polar due to its asymmetry and lone pair.
• SF₆ is nonpolar because of its symmetrical octahedral shape, which leads to an even distribution of charge.