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Ch.11 - Chemical Bonding II: Molecular Shapes, VSEPR & MO Theory
Chapter 11, Problem 40b

Determine the molecular geometry and sketch each molecule or ion, using the bond conventions shown in “Representing Molecular Geometries on Paper” in Section 11.4. b. SCl4

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Determine the total number of valence electrons in the molecule. Sulfur (S) has 6 valence electrons, and each chlorine (Cl) has 7 valence electrons. Since there are four Cl atoms, calculate the total valence electrons.
Identify the central atom, which is usually the least electronegative element. In this case, sulfur (S) is the central atom.
Use the valence shell electron pair repulsion (VSEPR) theory to determine the molecular geometry. Count the number of bonding pairs and lone pairs around the central atom.
For SCl4, there are four bonding pairs and one lone pair on the sulfur atom. According to VSEPR theory, this arrangement corresponds to a 'see-saw' molecular geometry.
Sketch the molecule using the bond conventions: draw the central sulfur atom, with two chlorine atoms in the plane of the paper, one chlorine atom above the plane (using a wedge), and one chlorine atom below the plane (using a dashed line). The lone pair is not shown in the sketch but affects the geometry.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

VSEPR Theory

Valence Shell Electron Pair Repulsion (VSEPR) Theory is a model used to predict the geometry of individual molecules based on the repulsion between electron pairs in the valence shell of the central atom. According to VSEPR, electron pairs will arrange themselves as far apart as possible to minimize repulsion, leading to specific molecular shapes.
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Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. It is determined by the number of bonding pairs and lone pairs of electrons around the central atom, which influences the overall shape, such as tetrahedral, trigonal bipyramidal, or octahedral, among others.
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Bond Angles

Bond angles are the angles formed between adjacent bonds in a molecule, which are influenced by the molecular geometry. These angles are critical for understanding the spatial arrangement of atoms and can affect the physical and chemical properties of the substance. For example, in SCl4, the bond angles will differ due to the presence of lone pairs affecting the shape.
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