Problem 155 - A Complete Resource Book in Chemistry for JEE Main

Question

Match the following: List I 1\. \(\mathrm{XeF}_{4}\) 2\. \(\mathrm{XeF}_{6}\) 3\. \(\mathrm{XeO}_{3}\) 4\. \(\mathrm{XeO}_{4}\) List II (i) distorted octahedral (ii) tetrahedral (iii) square planar (iv) pyramidal The correct matching is 1 2 3 4 (a) (iii) (i) (iv) (ii) (b) (ii) (i) (iii) (iv) (c) (i) (iii) (ii) (iv) (d) (iii) (iv) (i) (ii)

Step-by-Step Solution

Answer

The correct match is option (a): (iii), (i), (iv), (ii).

Step 1: Understanding List I: Molecule Geometries

In List I, the molecules have different geometry based on their chemical structure and the number of bonding and lone pairs around the central atom. Xenon usually forms compounds where each fluorine or oxygen replaces a lone pair.

Step 2: Analyzing XeF4 Geometry

XeF_{4} has xenon in the center with 4 fluorine atoms around it and 2 lone pairs on xenon. This electronic arrangement leads to a square planar shape, matching (iii) in List II.

Step 3: Analyzing XeF6 Geometry

XeF_{6} has 6 fluorine atoms around xenon, with one lone pair, resulting in a distorted octahedral shape since one position is occupied by a lone pair, matching (i) in List II.

Step 4: Analyzing XeO3 Geometry

In XeO_{3}, xenon is bonded to 3 oxygen atoms and has one lone pair, leading to a trigonal pyramidal geometry, which fits (iv) in List II.

Step 5: Analyzing XeO4 Geometry

XeO_{4} has four oxygens symmetrically arranged around xenon with no lone pairs, thus forming a tetrahedral shape, matching (ii) in List II.

Step 6: Identifying the Correct Match

From the analysis, the correct match is for XeF_{4} (iii), XeF_{6} (i), XeO_{3} (iv), and XeO_{4} (ii). Therefore, option (a) matches the sequence from List I to List II correctly.

Key Concepts

Molecular Geometry

Molecular geometry describes the three-dimensional arrangement of atoms within a molecule. It is influenced by the number of bonds and lone pairs around the central atom. In the case of xenon compounds like \(\mathrm{XeF}_{4}\), \(\mathrm{XeF}_{6}\), \(\mathrm{XeO}_{3}\), and \(\mathrm{XeO}_{4}\), the geometry is determined by the specific number of bonding pairs and lone pairs. Understanding the geometric structure is essential as it dictates the molecule's physical properties and reactivity. - \(\mathrm{XeF}_{4}\): Has a square planar geometry due to the presence of two lone pairs that repel each other and the four bonding pairs equally. - \(\mathrm{XeF}_{6}\): Exhibits a distorted octahedral shape since one position is occupied by a lone pair, leading to an uneven distribution. - \(\mathrm{XeO}_{3}\): Forms a trigonal pyramidal shape with three bonding pairs and one lone pair affecting its geometry. - \(\mathrm{XeO}_{4}\): Adopts a tetrahedral structure with no lone pairs interfering in the symmetric arrangement of oxygen atoms.

VSEPR Theory

VSEPR stands for Valence Shell Electron Pair Repulsion theory, a model used to predict the shape of molecules based on electron pair interactions. According to VSEPR theory, electron pairs arrange themselves to minimize repulsion, which dictates the geometry of the molecule.For xenon compounds: - In \(\mathrm{XeF}_{4}\), the two lone pairs on the xenon atom push against each other, creating a square planar geometry to minimize repulsion. - \(\mathrm{XeF}_{6}\), despite having a loan pair in the mix, strives for an octahedral arrangement. The lone pair distorts this symmetry, giving rise to a distorted octahedral shape.- For \(\mathrm{XeO}_{3}\), the lone pair causes a deviation from a simple trigonal planar to a trigonal pyramidal shape.- \(\mathrm{XeO}_{4}\) maintains a classic tetrahedral shape as there are no lone pairs to disrupt the symmetry.VSEPR theory is excellent for students to visualize and understand three-dimensional molecular structures by considering how electron pairs interact.

Xenon Compounds

Xenon, a noble gas, is unique because, under specific conditions, it forms compounds despite being typically inert. These compounds, when formed, exhibit intriguing geometries based on the presence of lone pairs and bound atoms.- \( \mathrm{XeF}_{4} \): Known for its stable square planar conformation due to two non-bonding electron pairs on xenon.- \( \mathrm{XeF}_{6} \): Presents a more complex structure with a distorted octahedral shape caused by one lone pair that modifies its arrangement significantly.- \( \mathrm{XeO}_{3} \): Forms a trigonal pyramidal structure due to the presence of a lone pair, making it highly reactive.- \( \mathrm{XeO}_{4} \): Features a perfect tetrahedral shape. With no lone pairs, the symmetrically arranged oxygen atoms grant \( \mathrm{XeO}_{4} \) its stability.These compounds illustrate the fascinating ways xenon's chemistry breaks the traditional understanding of noble gases.

Lone Pairs and Bond Pairs

The concept of lone pairs and bond pairs is crucial in understanding molecular shapes. Within a molecule, electrons can exist as bond pairs (engaged in chemical bonds) or lone pairs (not involved in bonding). Lone pairs occupy more space around the central atom compared to bond pairs because their electron clouds are not shared. This results in repulsions that affect the molecule's geometry.Examples in xenon halides and oxides:- In \( \mathrm{XeF}_{4} \), two lone pairs contribute to its square planar shape as they apply force that pushes bonding pairs together in the same plane.- \( \mathrm{XeF}_{6} \) has one lone pair impacting the octahedral symmetry, leading to a distorted form.- In \( \mathrm{XeO}_{3} \), the presence of a single lone pair results in a trigonal pyramidal shape, further distorting from what could trend towards a planar geometry.Understanding lone and bond pairs helps predict and explain the behavior and geometry of various molecules, especially those involving heavier elements like xenon.