Question

What is the electron-pair and molecular geometry around the central \(S\) atom in thionyl chloride, \(\operatorname{SOCl}_{2} ?\) What is the hybridization of sulfur in this compound?

Short answer

Electron-pair geometry: tetrahedral; Molecular geometry: trigonal pyramidal; Hybridization: \( sp^3 \).

Step-by-step solution

Determine the Total Number of Valence Electrons

Thionyl chloride, \( \text{SOCl}_2 \), consists of sulfur \( (S) \), oxygen \( (O) \), and two chlorine \( (Cl) \) atoms. Sulfur has 6 valence electrons, oxygen has 6, and each chlorine has 7, for a total of \( 6 + 6 + 2 \times 7 = 26 \) valence electrons.

Identify the Central Atom and Connect Atoms

Sulfur \( (S) \) is the central atom because it is less electronegative than oxygen and chlorine. Connect the sulfur atom with single bonds to the oxygen and each chlorine atom, using 6 electrons (3 bonds).

Distribute Remaining Electrons

Subtracting the 6 electrons used in the bonds, 20 electrons remain to distribute. First, satisfy the octet of oxygen by placing 6 more electrons around it; 14 electrons remain. Next, use 6 electrons to satisfy the octets of the chlorine atoms; 2 electrons remain to form a double bond between sulfur and oxygen.

Determine the Electron-Pair Geometry

There are 4 electron pairs around the sulfur atom: 1 double bond with oxygen and 2 single bonds with chlorine, plus 1 lone pair. This arrangement of electron pairs corresponds to a tetrahedral electron-pair geometry.

Determine the Molecular Geometry

Due to the presence of three bonded atoms and one lone pair on sulfur, the molecular geometry is trigonal pyramidal.

Identify Hybridization

Sulfur in \( \text{SOCl}_2 \) has 4 regions of electron density, which indicates \( sp^3 \) hybridization because 4 orbitals are mixed: one \( s \), and three \( p \) orbitals.

Key concepts

Understanding Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. In thionyl chloride, \( \text{SOCl}_2 \), the sulfur atom is central, bonded to an oxygen and two chlorine atoms. This creates a total of three bonds. In addition, there's one lone pair on sulfur. The presence of these three bonds and a lone pair gives the molecule a trigonal pyramidal geometry.

Why is this important? The shape influences molecular properties such as polarity, reactivity, and phase. For \( \text{SOCl}_2 \), the trigonal pyramidal shape leads to a polar molecule. The lone pair pushes down on the bonds, creating an asymmetrical shape, which in turn affects how the molecule interacts with other substances. Understanding the molecular shape helps in predicting how the compound will behave in chemical reactions.

In summary, identifying the molecular geometry is crucial for predicting the behavior and interactions of molecules.

Electron-Pair Geometry Explained

Electron-pair geometry considers the spatial arrangement of all electron pairs (bonding and lone pairs) around the central atom. For sulfur in \( \text{SOCl}_2 \), the electron-pair geometry is tetrahedral. This is because there are four areas of electron density: one double bond with oxygen, two single bonds with chlorine, and one lone pair.

You can picture this as a tetrahedron, where each corner represents one of the electron pairs. Even though only the bonded atoms are visible, the lone pair still influences the geometry. This arrangement is key to minimizing electron repulsion, which is the basis of VSEPR (Valence Shell Electron Pair Repulsion) theory. Thus, while the molecular shape is trigonal pyramidal, the electron-pair geometry remains tetrahedral.

• This geometry determines the molecular angles.
• It's crucial for predicting bond angles and overall shape.

Understanding electron-pair geometry gives insights into how molecules will arrange themselves in space.

Decoding Hybridization

Hybridization is the process of mixing atomic orbitals to form new hybrid orbitals ideal for pairing electrons. In \( \text{SOCl}_2 \), the sulfur atom has four regions of electron density, suggesting an \( sp^3 \) hybridization. This means one \( s \) orbital and three \( p \) orbitals from sulfur mix to form four identical \( sp^3 \) hybrid orbitals.

This hybridization is significant because it explains the molecule's shape and structure. The \( sp^3 \) orbitals are arranged tetrahedrally, allowing for optimal bond angles and spatial arrangement around the sulfur atom. Hybridization impacts the strength and length of bonds, influencing the molecule's stability and reactivity.

In essence, understanding hybridization helps to rationalize the molecular shape, bond characteristics, and overall behavior of molecules like \( \text{SOCl}_2 \) in various chemical contexts.