. Draw the Lewis dot structures, determine VSEPR shapes, give hybridization of the central atoms, and predict whether the molecules are polar. Put in order of increasing bond angle.
The Correct Answer and Explanation is:
Let’s break down each molecule:
1. SF2 (Sulfur Difluoride)
- Lewis Structure:
The sulfur atom (S) has 6 valence electrons, and each fluorine (F) atom has 7 valence electrons. The molecule consists of one sulfur atom bonded to two fluorine atoms. After placing the bonding pairs of electrons, we are left with lone pairs on sulfur and fluorine atoms. The Lewis structure would show sulfur at the center with two single bonds to fluorine, and each fluorine will have three lone pairs. The sulfur will have two lone pairs. - VSEPR Shape:
With 2 bonding pairs and 2 lone pairs on the sulfur atom, the shape is bent (AX2E2). - Hybridization:
The central sulfur atom undergoes sp3 hybridization. - Polarity:
Since the fluorine atoms are more electronegative than sulfur, the molecule will be polar due to the unequal sharing of electrons, resulting in a net dipole moment.
2. SF3+ (Sulfur Trifluoride Cation)
- Lewis Structure:
The sulfur atom (S) has 6 valence electrons, and each fluorine (F) atom has 7 valence electrons. In this cation, there is a positive charge, meaning one electron is lost. Therefore, we have 6 + 3(7) – 1 = 26 electrons to distribute. We place sulfur at the center, connected to three fluorine atoms, and account for formal charges. The Lewis structure shows sulfur with three bonds to fluorine and no lone pairs on sulfur, but each fluorine has three lone pairs. - VSEPR Shape:
The shape of SF3+ is trigonal planar (AX3). - Hybridization:
The central sulfur atom undergoes sp2 hybridization. - Polarity:
SF3+ is non-polar because the fluorine atoms are symmetrically arranged around the sulfur atom, and there is no net dipole moment due to symmetry.
3. SF6 (Sulfur Hexafluoride)
- Lewis Structure:
The sulfur atom (S) has 6 valence electrons, and each fluorine (F) atom has 7 valence electrons. There are 6 fluorine atoms, so the total number of electrons is 6 + 6(7) = 48 electrons. We place sulfur in the center and connect it to six fluorine atoms with single bonds. Each fluorine will have three lone pairs. The Lewis structure shows sulfur at the center with six single bonds to fluorine, and each fluorine atom has three lone pairs. - VSEPR Shape:
SF6 has a octahedral shape (AX6). - Hybridization:
The central sulfur atom undergoes sp3d2 hybridization. - Polarity:
SF6 is non-polar because the six fluorine atoms are symmetrically arranged around the sulfur atom, and there is no net dipole moment.
Order of Bond Angles (increasing):
- SF3+ (trigonal planar) has bond angles of 120°.
- SF2 (bent) has bond angles less than 120°, likely around 98° due to lone pair repulsion.
- SF6 (octahedral) has bond angles of 90° or 180°.
Thus, in order of increasing bond angle:
SF2 < SF3+ < SF6.
Summary:
- SF2 is polar, bent shape, sp3 hybridization.
- SF3+ is non-polar, trigonal planar shape, sp2 hybridization.
- SF6 is non-polar, octahedral shape, sp3d2 hybridization.
