Which statement correctly describes the sulfur tetrafluoride (SF4) molecule? Polar with a seesaw molecular geometry Nonpolar with a seesaw geometry Polar with a tetrahedral molecular geometry Nonpolar with a tetrahedral molecular geometry
The Correct Answer and Explanation is :
The correct answer is:
Polar with a seesaw molecular geometry
Explanation:
- Molecular Geometry:
The geometry of ( \text{SF}_4 ) is seesaw. This is determined by the VSEPR (Valence Shell Electron Pair Repulsion) theory:
- Sulfur (S) has 6 valence electrons.
- Fluorine (F) contributes 1 electron each (4 fluorine atoms add 4 electrons total).
- This results in 10 electrons or 5 electron pairs around sulfur.
- These electron pairs form a trigonal bipyramidal electron geometry. However, one of the five positions is occupied by a lone pair, which leads to a seesaw molecular geometry.
- Polarity:
( \text{SF}_4 ) is a polar molecule due to the following:
- The lone pair on sulfur is not symmetric, causing the molecule to have an uneven charge distribution.
- Fluorine atoms are highly electronegative, pulling electron density toward themselves.
- This asymmetry creates a net dipole moment, making the molecule polar.
- Nonpolar vs. Polar Comparison:
- A nonpolar molecule would require either symmetry in geometry (e.g., tetrahedral) or equal dipole moments canceling out.
- ( \text{SF}_4 ), due to its seesaw shape and the lone pair of electrons, lacks symmetry. This prevents the dipole moments from canceling out, making it polar.
- Why Not Tetrahedral?
Tetrahedral geometry occurs when there are four bonding pairs and no lone pairs around the central atom. ( \text{SF}_4 ) has one lone pair and four bonding pairs, so it is not tetrahedral.
In summary, ( \text{SF}_4 ) has a seesaw molecular geometry due to its lone pair of electrons, and it is polar due to its asymmetric shape and the electronegativity of fluorine atoms.