Problem 32 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

A list of species having the formula \(X Z_{4}\) is given below. \(\mathrm{XeF}_{4}, \mathrm{SF}_{4}, \mathrm{SiF}_{4}, \mathrm{BF}_{4}^{-},\mathrm{BrF}_{4}^{-},\left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}\right]^{2+},\left[\mathrm{FeCl}_{4}\right]^{2-},\left[\mathrm{CoCl}_{4}\right]^{2-}\) and \(\left[\mathrm{PtCl}_{4}\right]^{2-}\) Defining shape on the basis of the location of \(X\) and \(Z\) atoms, the total number of species having a square planar shape is

Step-by-Step Solution

Answer

There are 3 species with a square planar shape: \( \mathrm{XeF}_{4} \), \( \left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}\right]^{2+} \), and \( \left[\mathrm{PtCl}_{4}\right]^{2-} \).

Step 1: Identify Molecules with Potential Square Planar Shape

The given compounds are: \( \mathrm{XeF}_{4}, \mathrm{SF}_{4}, \mathrm{SiF}_{4}, \mathrm{BF}_{4}^{-}, \mathrm{BrF}_{4}^{-}, \left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}\right]^{2+}, \left[\mathrm{FeCl}_{4}\right]^{2-}, \left[\mathrm{CoCl}_{4}\right]^{2-}, \) and \( \left[\mathrm{PtCl}_{4}\right]^{2-} \). First, check the central atom and ligands in each compound.

Step 2: Determine Coordination and Geometry of Each Molecule

1. \( \mathrm{XeF}_{4} \): Xe has 6 electron pairs (4 bonding, 2 lone pairs) leading to a square planar shape.2. \( \mathrm{SF}_{4} \): S has a see-saw shape due to one lone pair.3. \( \mathrm{SiF}_{4} \): Si has a tetrahedral shape.4. \( \mathrm{BF}_{4}^{-} \): B has a tetrahedral shape.5. \( \mathrm{BrF}_{4}^{-} \): Br has 5 electron pairs (4 bonding, 1 lone pair) leading to a see-saw shape.6. \( \left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}\right]^{2+} \): Cu has a square planar shape.7. \( \left[\mathrm{FeCl}_{4}\right]^{2-} \): Fe has a tetrahedral shape.8. \( \left[\mathrm{CoCl}_{4}\right]^{2-} \): Co has a tetrahedral shape.9. \( \left[\mathrm{PtCl}_{4}\right]^{2-} \): Pt has a square planar shape.

Step 3: Count the Square Planar Molecules

From the previous analysis, the square planar molecules are \( \mathrm{XeF}_{4} \), \( \left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}\right]^{2+} \), and \( \left[\mathrm{PtCl}_{4}\right]^{2-} \).

Key Concepts

Molecular Geometry

Understanding molecular geometry is essential in inorganic chemistry. It describes the three-dimensional arrangement of atoms within a molecule.
This arrangement is determined by the number of electron pairs surrounding the central atom. In the molecules provided, different geometries are present due to varying numbers of bonding pairs and lone pairs of electrons.

• Tetrahedral geometry involves four bonding pairs and no lone pairs on the central atom, as seen in compounds like SiF₄ and BF₄^-.
• See-saw geometry occurs when there are four bonding pairs and one lone pair, influencing the molecular shape as seen in SF₄ and BrF₄^-.
• Square planar geometry is prominent in compounds with eight valence electrons forming four bonds and two lone pairs, like XeF₄ and PtCl₄^2-.

Square Planar Shape

The square planar shape is a significant topic in coordination chemistry, often appearing in complexes of transition metals. In this geometry, the central atom is surrounded by four ligand atoms forming the corners of a square plane.
This shape is typically found in d⁸ metal ions such as platinum and palladium, due to their electronic arrangement. The stability and realization of a square planar shape depend on the electronic configuration and the nature of the ligands involved.

• In XeF₄, xenon has two lone pairs that repel the bonded fluorine atoms into a planar arrangement.
• For \( \left[\mathrm{PtCl}_{4}\right]^{2-} \), the electronic arrangement favors this shape with platinum."}],"concept_headline":"Coordination Compounds","text":"Coordination compounds are complex molecules consisting of a central metal atom or ion bonded to surrounding ligands. These ligands can be ions or molecules with lone pairs of electrons.
  The central metal and its ligands together form a coordination sphere.
  • In \( \left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}\right]^{2+} \), copper forms a square planar complex with four ammonia molecules acting as ligands.
  • The \( \left[\mathrm{PtCl}_{4}\right]^{2-} \) ion is also a square planar complex, sharing platinum as the central atom with chlorine ligands."."}],"concept_headline":"Electron Pair Geometry","text":"Electron pair geometry considers both the bonding electron pairs and lone pairs surrounding a central atom. This is crucial for predicting molecular shapes using VSEPR (Valence Shell Electron Pair Repulsion) theory.
    In a tetrahedral arrangement, all electron pairs repel each other equally, leading to a symmetrical shape.
    • In the square planar geometry, such as in XeF₄, the electron pairs arrange to minimize repulsion, positioning lone pairs opposite each other above and below the planar structure.
    • For \( \left[\mathrm{PtCl}_{4}\right]^{2-} \), the electron pairing and metal-ligand interactions lead to a stable, low-energy square planar configuration."}]"}]}]}]}