Problem 106 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is a correct pair with respect to molecular formula of a xenon compound and the hybridization state of xenon in it? (a) \(\mathrm{XeF}_{2}, \mathrm{sp}\) (b) \(\mathrm{XeF}_{4}, \mathrm{sp}^{2}\) (c) \(\mathrm{XeF}_{4}, \mathrm{sp}^{3}\) (d) \(\mathrm{XeF}_{2}, \mathrm{sp}^{3} \mathrm{~d}\)

Step-by-Step Solution

Answer

Option (d) \( \mathrm{XeF}_2, \mathrm{sp}^3\mathrm{d} \) is correct.

Step 1: Understanding Xenon's Valence Electrons

Xenon is a noble gas, and it has 8 valence electrons in its outer shell. When xenon forms compounds, these electrons can be used to form bonds with other elements, such as fluorine.

Step 2: Analyzing Option (a) \( \mathrm{XeF}_2, \mathrm{sp} \)

In \( \mathrm{XeF}_2 \), xenon is bonded to two fluorine atoms and has 3 lone pairs. This results in a total of 5 pairs: 2 bonding pairs and 3 lone pairs, which leads to a linear shape and the hybridization being \( \mathrm{sp}^3\mathrm{d} \), not \( \mathrm{sp} \).

Step 3: Analyzing Option (b) \( \mathrm{XeF}_4, \mathrm{sp}^2 \)

In \( \mathrm{XeF}_4 \), xenon is bonded to four fluorine atoms and has 2 lone pairs. This leads to 6 pairs: 4 bonding pairs and 2 lone pairs, resulting in a square planar shape and the hybridization being \( \mathrm{sp}^3\mathrm{d}^2 \), not \( \mathrm{sp}^2 \).

Step 4: Analyzing Option (c) \( \mathrm{XeF}_4, \mathrm{sp}^3 \)

Again, in \( \mathrm{XeF}_4 \), xenon has 6 pairs: 4 bonds with fluorine and 2 lone pairs, leading to \( \mathrm{sp}^3\mathrm{d}^2 \) hybridization, not \( \mathrm{sp}^3 \).

Step 5: Analyzing Option (d) \( \mathrm{XeF}_2, \mathrm{sp}^3\mathrm{d} \)

In \( \mathrm{XeF}_2 \), xenon with its two bonds to fluorine atoms and three lone pairs forms 5 pairs overall, which corresponds to an \( \mathrm{sp}^3\mathrm{d} \) hybridization, matching the description.

Key Concepts

Molecular Formula

The molecular formula provides a concise representation of a compound, revealing the types and numbers of atoms present in a molecule. In the context of xenon compounds, the molecular formula helps us understand the arrangement and ratio of atoms within the compound.
For instance:

• **XeF₂** indicates a xenon atom bonded to two fluorine atoms.
• **XeF₄** signifies a xenon atom connected to four fluorine atoms.

This information is crucial because it sets the stage for predicting molecular geometry and hybridization, which are derived from the number of atoms and electron pairs around the central atom, xenon.

Hybridization

Hybridization is a concept used to explain the arrangement of bonding in molecules. It describes how atomic orbitals mix to form new hybrid orbitals, which can house pairs of electrons, serving as bonding or lone pair regions around the central atom.
In xenon compounds:

• **XeF_{2**: Xenon uses 5 orbitals which combine into sp³d hybridization, forming a linear shape.}
• **XeF_{4**: The sp³d² hybridization is employed, resulting in a square planar shape due to the six pairs (4 bonds and 2 lone pairs).}

Knowing the hybridization allows us to predict molecular shapes and angles, offering insights into the compound's physical properties.

Valence Electrons

Valence electrons are the outermost electrons of an atom and are integral in bonding. For xenon, a noble gas, it has a stable octet with 8 valence electrons.
When forming compounds like XeF₂ or XeF₄:

• **XeF_{2**: Xenon shares two of its electrons with fluorine atoms, involving three lone pairs in the remaining orbitals.}
• **XeF_{4**: Xenon shares four electrons, leaving two lone pairs to complete its octet.}

Understanding valence electrons is critical in assessing how and why xenon forms specific compounds, despite its typical inertness.

Bonding Pairs

Bonding pairs refer to the pairs of electrons involved in bonds between atoms. These are significant in determining the molecular geometry. In xenon compounds:

• **XeF_{2**: Features 2 bonding pairs and 3 lone pairs, organizing themselves into a linear configuration due to the electron repulsion.}
• **XeF_{4**: Contains 4 bonding pairs and 2 lone pairs, resulting in a square planar shape.}

Identifying the number of bonding pairs helps predict shapes and angles between bonds, making it easier to visualize how the molecule looks and behaves. This understanding contributes to predicting molecular interactions and reactivity.