Question

What is the hybridization state of \(\mathrm{Si}\) (a) in \(\mathrm{SiH}_{4}\) and (b) in \(\mathrm{H}_{3} \mathrm{Si}-\mathrm{SiH}_{3} ?\)

Short answer

In both SiH4 and H3Si-SiH3, Si is sp3 hybridized.

Step-by-step solution

Understanding Hybridization

Hybridization refers to the mixing of atomic orbitals in an atom to form new hybrid orbitals that can form covalent bonds. The hybridization state of an atom can often be deduced by considering the number and types of bonds it forms.

Determine Hybridization in SiH4

In \mathrm{SiH}_{4} \, Silicon (Si) is bonded to four hydrogen atoms. When an atom makes four sigma bonds, it uses an sp\(^3\) hybridization. Therefore, the hybridization state of Si in \mathrm{SiH}_{4} \, is sp\(^3\).

Determine Hybridization in H3Si-SiH3

In \mathrm{H}_{3}Si-\mathrm{SiH}_{3} \, each Si atom is bonded to three hydrogen atoms and one Si atom, making a total of four sigma bonds for each silicon atom. Like in the previous compound, forming these four sigma bonds requires an sp\(^3\) hybridization. Thus, the hybridization state of each Si in \mathrm{H}_{3}Si-\mathrm{SiH}_{3} \, is sp\(^3\).

Key concepts

sp3 Hybridization

In chemistry, hybridization is an essential concept that explains how different atomic orbitals combine to form new ones called hybrid orbitals. These hybrid orbitals can accommodate electron pairs used in bonding. When an atom forms four sigma bonds, like in molecules such as \(\text{SiH}_4\) and \(\text{H}_3\text{Si}-\text{SiH}_3\), it typically undergoes \(\text{sp}^3\) hybridization.

\(\text{sp}^3\) hybridization involves the mixing of one s orbital and three p orbitals from the same atom. This process creates four equivalent hybrid orbitals that are organized in a tetrahedral shape. Each of these orbitals can overlap with orbitals from other atoms to form covalent bonds. This structure results in a stable configuration, allowing the molecule to maintain a sturdy 3D arrangement.

• \(\text{sp}^3\) hybridization results in tetrahedral geometry.
• All bond angles in \(\text{sp}^3\) hybridization are approximately 109.5 degrees.
• Each hybrid orbital can form a sigma bond.

Sigma Bonds

Sigma bonds, symbolized by the Greek letter \(\sigma\), are the strongest type of covalent bonds. They form when atomic orbitals overlap end-to-end, allowing electron density to be concentrated between the nuclei of the bonding atoms. In the context of \(\text{sp}^3\) hybridization, each hybridized orbital can form a sigma bond with another atom.

In molecules like \(\text{SiH}_4\) and \(\text{H}_3\text{Si}-\text{SiH}_3\), \(\sigma\) bonds play a crucial role in holding the atoms together in a stable manner. The simplicity and symmetry of sigma bonds contribute to the strength and integrity of the chemical structures. These bonds are also characterized by their rotational symmetry, allowing atoms connected by sigma bonds to rotate around the bond axis.

• \(\sigma\) bonds form by overlapping orbitals along the bond axis.
• They provide rotational freedom along the bond axis.
• These bonds contribute significantly to molecular stability.

Covalent Bonds

Covalent bonds are fundamental in chemistry for the formation of molecules. They occur when two atoms share a pair of electrons, enabling them to achieve a full outer electron shell. These shared electrons are situated in overlapping orbitals that bond the atoms together.

Different types of covalent bonds can exist depending on how the orbitals overlap. The most common are single and sigma bonds, such as those found in \(\text{sp}^3\) hybridized molecules like \(\text{SiH}_4\). Each silicon atom forms covalent bonds with hydrogen atoms by sharing electrons, which results in a full valence shell and stable molecule formation. Through covalent bonding, molecules like \(\text{H}_3\text{Si}-\text{SiH}_3\) achieve their distinct structures.

• Covalent bonds involve electron sharing between atoms.
• They provide molecules with stability and shape.
• Most covalent bonds are examples of sigma bonds.

Atomic Orbitals

Atomic orbitals are regions around an atomic nucleus where electrons are likely to be found. These orbitals can have different shapes and energy levels, typically categorized into s, p, d, and f orbitals based on quantum numbers. Understanding these orbitals is crucial for grasping how chemical bonds form.

For example, in \(\text{sp}^3\) hybridization, one s orbital and three p orbitals from the same atom mix to form four hybrid orbitals. These new hybrid orbitals adopt a tetrahedral shape that facilitates the formation of effective covalent sigma bonds. Each atomic orbital can hold up to two electrons, which engage in bonding with other atoms through orbital overlap.

• Orbitals are areas where electrons are most probable to be found.
• They come in different shapes: spherical (s) and dumbbell-shaped (p).
• Hybridization can transform atomic orbitals into hybrid orbitals.