Draw the Lewis structure for SF6 and then answer the following questions that follow.
-Do not include overall ion charges or formal charges in your drawing.
Questions:
1). What is the electron-pair geometry for S in SF6?
2). What is the shape (molecular geometry) of SF6?
The Correct Answer and Explanation is :
Lewis Structure of SF₆ (Sulfur Hexafluoride)
To draw the Lewis structure for SF₆:
- Count valence electrons:
- Sulfur (S) has 6 valence electrons.
- Each Fluorine (F) has 7 valence electrons.
- Since there are 6 Fluorine atoms, total electrons from Fluorine = 6 × 7 = 42.
- Total valence electrons = 6 (S) + 42 (F) = 48.
- Determine the central atom:
- Sulfur is the least electronegative and will be the central atom.
- Distribute electrons:
- Place six fluorine atoms around sulfur.
- Connect each fluorine to sulfur with a single bond (each bond uses 2 electrons).
- Each fluorine needs 3 lone pairs to complete its octet.
- Check formal charges and octet rule:
- Sulfur has 6 bonding pairs (12 electrons), exceeding the octet rule due to its ability to expand its valence shell (period 3 element).
- Each fluorine has 8 electrons (1 bond + 6 non-bonding), fulfilling the octet rule.
- No formal charges are needed.
Lewis Structure Image
I will generate the Lewis structure image for SF₆.
Answers to Questions
1) What is the electron-pair geometry for S in SF₆?
The electron-pair geometry for sulfur in SF₆ is octahedral. This is because sulfur has six bonding pairs and no lone pairs, making the electron pairs arrange themselves symmetrically around the central atom in an octahedral fashion.
2) What is the shape (molecular geometry) of SF₆?
The molecular geometry of SF₆ is also octahedral.
Explanation (300 Words)
Sulfur hexafluoride (SF₆) is an AX₆ type molecule, following the VSEPR (Valence Shell Electron Pair Repulsion) theory. In SF₆, sulfur (S) is the central atom, and it is surrounded by six fluorine (F) atoms. The molecule has six bonding pairs and no lone pairs on sulfur. Because of this, the six bonds repel each other equally, and the molecule adopts a perfectly symmetrical octahedral geometry.
The octahedral geometry means that:
- Bond angles are 90° between adjacent fluorine atoms.
- The structure is highly stable and symmetrical.
- There are no lone pairs on sulfur, meaning there is no distortion in shape.
Sulfur can expand its octet because it is in period 3 of the periodic table, allowing it to accommodate more than 8 valence electrons. This is why sulfur is able to form six bonds instead of the usual two (as seen in compounds like SO₂).
The octahedral shape of SF₆ makes it a nonpolar molecule even though each S-F bond is polar. This is due to the symmetrical distribution of charge, leading to the cancellation of dipole moments.
SF₆ is widely used as an electrical insulator in high-voltage equipment and as a shielding gas in various industries. Its non-reactive nature and stability make it an ideal choice for these applications.