Draw the lewis structure for SF3 , and indicate how many electron groups are around the central sulfur atom in SF3 , and What is electron geometry and molecular geometry? (Note: You need to show complete solution map by drawing the Lewis structure of SF, in your Quiz 3 Honor Pledge to receive Full credit).
The correct answer and explanation is:
To draw the Lewis structure for SF₃ (sulfur trifluoride), we will go through the following steps:
Step 1: Determine the Total Number of Valence Electrons
- Sulfur (S): Sulfur is in Group 16 of the periodic table, so it has 6 valence electrons.
- Fluorine (F): Fluorine is in Group 17, so each fluorine atom has 7 valence electrons. Since there are three fluorine atoms, we multiply by 3: 7 * 3 = 21 valence electrons from fluorine.
So, the total number of valence electrons for SF₃ is:
6 (from sulfur) + 21 (from fluorine) = 27 valence electrons.
Step 2: Draw the Skeleton Structure
Place sulfur as the central atom since it is less electronegative than fluorine. Connect each fluorine atom to the sulfur atom with a single bond (which uses 2 electrons per bond).
Step 3: Distribute the Electrons
- Each single bond between sulfur and fluorine uses 2 electrons, so 3 bonds will use 6 electrons (3 bonds * 2 electrons = 6 electrons).
- We have 27 total electrons, so after placing the bonds, we are left with 27 – 6 = 21 electrons.
- Distribute these remaining 21 electrons as lone pairs around the fluorine atoms first. Each fluorine needs 3 lone pairs (6 electrons) to satisfy the octet rule.
- After placing 3 lone pairs on each of the three fluorine atoms (18 electrons), we have 3 electrons remaining, which will go to the sulfur atom.
Step 4: Assign Lone Pairs to the Central Atom
Sulfur can have an expanded octet, so it can accommodate more than 8 electrons. Place the remaining 3 electrons as a lone pair on the sulfur atom.
Step 5: Final Structure
The Lewis structure is as follows:
- Sulfur is the central atom with a lone pair of electrons.
- Each fluorine is attached by a single bond and has 3 lone pairs.
Step 6: Electron Groups and Geometry
- The central sulfur atom has three single bonds to fluorine and one lone pair of electrons, so there are 4 electron groups around sulfur (3 bonding groups + 1 lone pair).
- The electron geometry is based on the number of electron groups around the central atom. With 4 electron groups, the electron geometry is tetrahedral.
- The molecular geometry is based on the positions of the atoms, excluding the lone pair. With 3 bonding groups and 1 lone pair, the molecular geometry is trigonal pyramidal.
Conclusion
- The Lewis structure for SF₃ shows sulfur with three bonds to fluorine atoms and one lone pair on sulfur.
- There are 4 electron groups around the sulfur atom, which gives the molecule a tetrahedral electron geometry.
- The molecular geometry is trigonal pyramidal due to the lone pair on sulfur.
This solution involves a tetrahedral arrangement, which corresponds to a trigonal pyramidal shape for the molecular geometry due to the presence of the lone pair. The central sulfur atom’s expanded octet allows it to accommodate more than 8 electrons.