Question

The type of hybridization of boron in diborane is (a) \(s p-\) hybridization (b) \(s p^{2}\)-hybridization (c) \(s p^{3}\)-hybridization (d) \(s p^{3} d^{2}\)-hybridization.

Short answer

The type of hybridization of boron in diborane is (c) sp3-hybridization.

Step-by-step solution

Understanding Hybridization

Hybridization is the concept of mixing atomic orbitals to create new hybrid orbitals suitable for the pairing of electrons to form chemical bonds in molecular compounds. The type of hybridization depends on the number of atomic orbitals mixed and the geometry of the molecule.

Analyzing the Structure of Diborane

Diborane (B2H6) has a structure in which each boron atom has four orbitals involved in bonding. The two boron atoms are bonded to four terminal hydrogen atoms and there are two bridging hydrogen atoms that share electrons with both boron atoms.

Determining the Hybridization of Boron in Diborane

Boron contributes its three valence electrons, and in order to form four bonds (two with terminal hydrogens and two with bridging hydrogens), it mixes its s orbital with three p orbitals. This results in four sp3 hybrid orbitals that accommodate the electron pairs that bond with the hydrogens.

Key concepts

SP3 Hybridization

The concept of sp3 hybridization is fundamental when exploring the diverse bonding scenarios in chemical compounds. It occurs when one s orbital mixes with three p orbitals to form four equivalent hybrid orbitals. This hybridization is a cornerstone in understanding how atoms like boron in diborane create bonds.

In an atom that undergoes sp3 hybridization, these newly formed sp3 orbitals have a tetrahedral arrangement with an angle of 109.5 degrees between them, which is central to predicting the geometry of molecules. For instance, in the case of diborane (B2H6), each boron atom undergoes sp3 hybridization. Although boron only has three electrons available for bonding, it manages to form bonds with four hydrogen atoms—two to terminal hydrogens and two to a pair of bridging hydrogens. This seemingly puzzling scenario is key to understanding the bonding in diborane.

The ability of the boron atoms to extend their valence shell and form additional bonds through sp3 hybridization is fascinating. It allows the creation of complex structures that defy the simplistic octet rule, and is indicative of the flexibility of the chemical bonding framework.

Chemical Bonding

At the heart of molecules is chemical bonding, the force that holds atoms together in compounds. Chemical bonds are formed when electrons are shared, gained, or lost between atoms. For diborane, the type of bonding is complex due to the presence of both regular bonds to terminal hydrogens and three-center two-electron (3c-2e) bonds to bridging hydrogens.

In traditional covalent bonds, two atoms share a pair of electrons. However, with diborane's bridging hydrogens, two electrons are shared among three atoms—two boron and one hydrogen—which is known as a three-center two-electron bond. This type of bonding is less common and is an example of the intricacies of chemical bonds beyond the simple sharing or transferring of electrons.

Understanding these less orthodox bonding types is crucial for comprehending the structure and reactivity of complex molecules such as diborane. It underscores the idea that not all bonds are created equal, and that chemical bonding can range from the simple to the highly complicated, often influenced by the orbital hybridization of the involved atoms.

Molecular Geometry

The concept of molecular geometry describes the three-dimensional shape of a molecule, governed by the spatial arrangement of its atoms. Molecular geometry is not only visually intriguing but also has profound implications for the properties and behavior of molecules.

In diborane, the molecular geometry around each boron atom is initially predicted to be tetrahedral due to sp3 hybridization, yet the overall geometry of the molecule does not strictly conform to this. With its unique pair of bridging hydrogen atoms, diborane assumes a shape that is somewhat at odds with the standard tetrahedral shape.

The presence of the three-center two-electron bonds causes a slight distortion, leading to a fascinating and less common geometry. These bridging bonds actually have a key role in defining the molecular geometry and overall structure of the molecule. When learning about molecular geometry, it is important to consider not just the positions of atoms, but also how the types of bonds and hybridization of orbitals affect the overall shape of the molecule.