Question

Among the following molecules, \(\mathrm{p}-\mathrm{p}\) overlap takes place in (a) \(\mathrm{H}_{2}\) (b) \(\mathrm{BeCl}_{2}\) (c) \(\mathrm{F}_{2}\) (d) HF

Short answer

Question: Identify the molecule in which p-p orbital overlap takes place among the following molecules: (a) H2, (b) BeCl2, (c) F2, and (d) HF. Answer: (c) F2

Step-by-step solution

Analyze Hydrogen Molecule (H2)

In H2 molecule, each hydrogen atom has one electron in its 1s orbital. For both hydrogen atoms to share their electrons and form a bond, the 1s orbitals of the two hydrogen atoms will overlap. Thus, the bond formation in H2 is due to the overlap of two 1s orbitals (s-s overlap).

Analyze Beryllium Chloride Molecule (BeCl2)

In BeCl2 molecule, the central atom, beryllium, has two valence electrons in its 2s orbital. Each chlorine atom has seven valence electrons, with three in 2p orbitals and two in 2s orbitals. Beryllium forms two bonds with two chlorine atoms by sharing its two 2s electrons. In this case, the bond formation is due to the overlap of one 2s orbital from beryllium and one 3p orbital from each chlorine atom (s-p overlap).

Analyze Fluorine Molecule (F2)

In F2 molecule, each fluorine atom has seven valence electrons, with three electrons in 2p orbitals and two pairs of electrons in the 2s orbitals. For both fluorine atoms to share a pair of electrons and form a bond, the 2p orbitals of two fluorine atoms will overlap. Thus, the bond formation in F2 is due to the overlap of two 2p orbitals (p-p overlap).

Analyze Hydrogen Fluoride Molecule (HF)

In the HF molecule, hydrogen has one electron in its 1s orbital, and fluorine has seven valence electrons. Hydrogen shares its 1s electron with one unpaired electron in the 2p orbital of fluorine to form a bond. The bond formation in HF is due to the overlap of one 1s orbital of hydrogen and one 2p orbital of fluorine (s-p overlap).

Identify the Molecule with p-p Overlap

Among the molecules, the F2 molecule has a bond formed by the overlap of two 2p orbitals (p-p overlap). Thus, the correct answer is (c) F2.

Key concepts

p-p Orbital Overlap

In molecular orbital theory, the concept of p-p orbital overlap is crucial to understand how molecules form. When two atoms share electrons through the overlap of their p orbitals, it creates a strong bond due to the effective sharing of electron density.

• The p orbital is dumbbell-shaped and can hold a maximum of six electrons.
• This type of overlap usually occurs when both participating atoms have unpaired electrons in their p orbitals.

For example, the fluorine molecule (F2) exhibits this type of bond. Each fluorine atom contributes an electron from its 2p orbital. The overlap of these orbitals facilitates the sharing of electrons, resulting in a bond that's both stable and directional.
In general, p-p overlaps lead to the formation of pi bonds, which are essential in double and triple bonds within molecules.

s-s Orbital Overlap

s-s orbital overlap is one of the simplest forms of bond formation. It occurs when two s orbitals from different atoms come together, sharing their electrons.

• The s orbital is spherical and can accommodate up to two electrons.
• This type of overlap is shorter-ranged because of the close proximity needed for s orbitals to interact effectively.

A classic example of s-s overlap is found in the hydrogen molecule (H2), where each hydrogen atom contributes its 1s electron to form a sigma bond.
The electrons become delocalized within the created molecular orbital, allowing the hydrogen atoms to bond efficiently.

s-p Orbital Overlap

In scenarios where s and p orbitals overlap, we encounter s-p orbital overlap. This occurs widely in many molecules where one atom's s orbital interacts with another atom's p orbital.

• The s orbital must have an unpaired electron to participate in bonding.
• Meanwhile, the p orbital also needs an unpaired electron ready to engage in bonding.

For instance, in the hydrogen fluoride molecule (HF), hydrogen's 1s electron overlaps with one of fluorine's 2p electrons. The result is a polar covalent bond that features both directional characteristics and electron sharing.
This overlap is crucial for a wide variety of molecular configurations, contributing to the diversity of chemical structures.

Bond Formation

Bond formation in molecular orbital theory involves the overlapping of atomic orbitals to result in new molecular orbitals that hold electrons in a shared state. There are different types of orbital overlaps that contribute to bond formation.

• s-s overlap: Forms a sigma bond, as seen in the H2 molecule.
• p-p overlap: Results in pi bonds, crucial for multiple bonds like those in the F2 molecule.
• s-p overlap: Produces bonds such as those in BeCl2 and HF, typically leading to polar covalent characteristics.

Each type of bond overlap is governed by the shape, energy, and orientation of the participating orbitals. When these factors align optimally, electrons are shared, leading to stable molecular configurations.