Complete the following table: a. Draw Lewis structures for each of the following molecules. b. Describe the electron pair geometry (EPG). c. Describe the molecular geometry (MG). d. Give the hybridization of the central atom (sp, sp2, etc.). e. State the polarity. The first or underlined atom is the central atom. Lewis Structure 1: SCI2 EPG: MG: Hybr.: Polar? 2. TeO2 3. NO2- 4. SnBr3 5. SO2 6. XeF2 Explain this variation in bond angles.
The Correct Answer and Explanation is:
Here is the completed table with the correct answers.
| Lewis Structure | EPG (Electron Pair Geometry) | MG (Molecular Geometry) | Hybr. (Hybridization) | Polar? | |
| 1) SCl₂ | Sulfur is the central atom, single-bonded to two chlorine atoms. The sulfur atom also has two lone pairs of electrons. | Tetrahedral | Bent | sp³ | Polar |
| 2) TeO₄²⁻ | Tellurium is the central atom, bonded to four oxygen atoms. The structure is a resonance hybrid, best shown with two Te-O single bonds and two Te=O double bonds. The ion has an overall 2- charge. | Tetrahedral | Tetrahedral | sp³ | Nonpolar |
| 3) NO₂⁺ | Nitrogen is the central atom, double-bonded to two oxygen atoms. The ion has a linear shape and an overall 1+ charge. | Linear | Linear | sp | Nonpolar |
| 4) SnBr₃⁻ | Tin is the central atom, single-bonded to three bromine atoms. The tin atom also has one lone pair of electrons. The ion has an overall 1- charge. | Tetrahedral | Trigonal Pyramidal | sp³ | Polar |
| 5) SO₂ | Sulfur is the central atom, bonded to two oxygen atoms. The structure is a resonance hybrid of two forms, each with one S-O single bond and one S=O double bond. The sulfur atom has one lone pair. | Trigonal Planar | Bent | sp² | Polar |
| 6) XeF₂ | Xenon is the central atom, single-bonded to two fluorine atoms. The xenon atom has an expanded octet with three lone pairs of electrons in the equatorial positions. | Trigonal Bipyramidal | Linear | sp³d | Nonpolar |
Explanation
The properties of each molecule or ion are determined by its electronic and atomic arrangement, which can be predicted using a systematic approach.
First, the total number of valence electrons is calculated. These electrons are used to draw a Lewis structure that satisfies the octet rule for most atoms, with exceptions for elements like xenon which can have an expanded octet.
The Lewis structure reveals the number of electron groups (bonding pairs and lone pairs) around the central atom. The VSEPR (Valence Shell Electron Pair Repulsion) theory states that these electron groups arrange themselves to be as far apart as possible, defining the electron pair geometry (EPG). The hybridization of the central atom is directly related to the number of electron groups: two groups correspond to sp hybridization, three to sp², four to sp³, and five to sp³d.
The molecular geometry (MG) describes the arrangement of only the atoms, ignoring the lone pairs. When no lone pairs are on the central atom, the MG is the same as the EPG. However, lone pairs occupy space and repel bonding pairs, altering the shape. For example, SCl₂ and SnBr₃⁻ both have a tetrahedral EPG (4 electron groups), but the presence of lone pairs results in bent and trigonal pyramidal molecular geometries, respectively.
Finally, polarity depends on both bond polarity and molecular symmetry. A molecule with polar bonds can be nonpolar overall if its geometry is symmetrical, causing the bond dipoles to cancel each other out. This is observed in TeO₄²⁻ (tetrahedral), NO₂⁺ (linear), and XeF₂ (linear). In contrast, asymmetrical geometries, such as the bent shape of SCl₂ and SO₂, or the trigonal pyramidal shape of SnBr₃⁻, result in a net dipole moment, making the species polar.
