Question

A molecule in which \(s p^{2}\) hybrid orbitals are used by the central atom in forming covalent bonds is (a) \(\mathrm{PCl}_{5}\) (b) \(\mathrm{N}_{2} ;\) (c) \(\mathrm{SO}_{2} ;\) (d) \(\mathrm{He}_{2}\)

Short answer

The molecule in which \(sp^{2}\) hybrid orbitals are used by the central atom in forming covalent bonds is \(\mathrm{SO}_{2}\).

Step-by-step solution

Structure of PCl5

The central atom in \(\mathrm{PCl}_{5}\) is Phosphorus (P). It has 5 valence electrons, and it forms 5 sigma bonds with 5 Chlorine (Cl) atoms. There are no lone pairs on Phosphorus. So, the hybridization is \(sp^{3}d\), not \(sp^{2}\).

Structure of N2

The molecule \(\mathrm{N}_{2}\) is composed of two Nitrogen (N) atoms. Each Nitrogen atom forms one sigma bond with the other Nitrogen atom and two pi bonds. So, no \(sp^{2}\) hybridization here. The hybridization is \(sp\).

Structure of SO2

The central atom in \(\mathrm{SO}_{2}\) is Sulphur (S). It forms two sigma bonds with two Oxygen (O) atoms and has one lone pair. Hence, it's hybridization is \(sp^{2}\). Therefore, \(\mathrm{SO}_{2}\) is the molecule in which \(sp^{2}\) hybrid orbitals are used by the central atom in forming covalent bonds.

Structure of He2

The molecule \(\mathrm{He}_{2}\) does not exist because Helium (He) is a noble gas and it does not form covalent bonds with other atoms. So, it doesn't undergo hybridization.

Key concepts

Hybridization

Hybridization is a concept in chemistry that describes the mixing of atomic orbitals to form new hybrid orbitals. These hybrid orbitals have different energies and shapes than the original atomic orbitals. The purpose of hybridization is to explain how atoms form bonds and how they can orient in space for optimal bonding.

To understand hybridization, consider atoms like carbon, nitrogen, and sulfur which can form multiple bonds in molecules. In these cases, atomic orbitals such as s, p, and sometimes d orbitals mix together to form equivalent hybrid orbitals.

By doing so, hybridization allows atoms to form stronger covalent bonds as it facilitates the overlap of orbitals between bonding atoms, leading to a more stable molecular structure.

• It helps in the prediction of molecular geometry.
• It accounts for the equivalent bond angles found in many molecules.

Ultimately, hybridization is essential in explaining the structures and bonding of covalent molecules.

sp2 Hybrid Orbitals

The concept of sp2 hybrid orbitals is crucial when discussing certain molecular geometries. When an atom undergoes sp2 hybridization, it combines one s orbital and two p orbitals to form three equivalent sp2 hybrid orbitals.

These sp2 orbitals have a trigonal planar arrangement, which means they are 120 degrees apart in a planar structure. This arrangement allows the atom to form three sigma bonds. The leftover p orbital is perpendicular to the plane of sp2 orbitals and can participate in forming pi bonds.

For example, in the sulfur dioxide (\(\mathrm{SO}_{2}\)) molecule, the central sulfur atom uses sp2 hybrid orbitals to form sigma bonds with oxygen atoms, while the unhybridized p orbital is involved in making a pi bond.

• This type of hybridization results in a molecular shape that is flat and symmetrical, typical for many organic compounds.
• sp2 hybridization is often seen in molecules with double bonds where one of the bonds is a sigma bond and the other is a pi bond.

Covalent Bonds

Covalent bonds are a type of chemical bond formed by the sharing of electron pairs between atoms. This sharing allows each atom to achieve a more stable electron configuration, often resembling a noble gas configuration. Covalent bonding is prevalent in organic compounds and many molecular substances like water or sulfur dioxide.

Covalent bonds can be single, double, or triple, depending on the number of shared electron pairs.

• Single covalent bonds involve one electron pair.
• Double covalent bonds involve two electron pairs.
• Triple covalent bonds involve three electron pairs.

In molecules like \(\mathrm{SO}_{2}\), sulfur forms covalent bonds with oxygen atoms. These bonds are partly distributed using sp2 hybrid orbitals resulting in a mix of sigma and pi bonds. Covalent bonds are characterized by bond strength, which depends on how much orbital overlap occurs during bond formation.

Molecular Structure

Molecular structure refers to the three-dimensional arrangement of atoms within a molecule. The shape of a molecule strongly influences its physical and chemical properties. Understanding molecular structure is vital in determining how molecules interact with each other, including reaction mechanisms, polarity, and molecular recognition.

The structure is often governed by the type of hybridization that has occurred in the central atom.

• Molecules with sp2 hybridization, such as \(\mathrm{SO}_{2}\), adopt a trigonal planar shape, enhancing their reactivity in certain chemical environments.
• Knowing the molecular structure helps in predicting how the molecule will behave in various chemical reactions.

For example, the planar structure of \(\mathrm{SO}_{2}\), due to sp2 hybridization, is a factor in its reactivity and properties as a molecule that causes acid rain. Such structural insights enable chemists to design and synthesize molecules for desired outcomes.