Analyzing Planar Molecular Geometries
The question asks us to identify the set containing only planar species. A planar species is one where all the constituent atoms are located within the same plane. We can determine the shape of molecules using the Valence Shell Electron Pair Repulsion (VSEPR) theory, which helps predict the geometry based on minimizing electron pair repulsions around the central atom.
Determining Molecular Geometry Using VSEPR Theory
The VSEPR theory involves the following steps:
- Identify the central atom.
- Calculate the total number of valence electrons of the central atom.
- Determine the number of bonding pairs (BP) and lone pairs (LP) around the central atom.
- Calculate the steric number (SN), where SN = BP + LP.
- Determine the electron geometry based on SN.
- Determine the molecular geometry by considering the spatial arrangement of bonded atoms only.
- Assess if the molecular geometry is planar.
Analysis of Chemical Species
Let's analyze the geometry and planarity of each species mentioned:
Xenon Tetrafluoride ($XeF_4$)
- Central Atom: Xenon (Xe)
- Valence electrons of Xe: 8
- Bonding Pairs (BP) with Fluorine (F): 4
- Lone Pairs (LP): (8 valence electrons - 4 bonding pairs * 2 electrons/pair) / 2 = 4 / 2 = 2
- Steric Number (SN): 4 (BP) + 2 (LP) = 6
- Electron Geometry: Octahedral
- Molecular Geometry: Square Planar (4 BP and 2 LP arranged opposite each other)
- Planarity: Yes
Boron Trifluoride ($BF_3$)
- Central Atom: Boron (B)
- Valence electrons of B: 3
- Bonding Pairs (BP) with Fluorine (F): 3
- Lone Pairs (LP): (3 valence electrons - 3 bonding pairs * 2 electrons/pair) / 2 = 0 / 2 = 0
- Steric Number (SN): 3 (BP) + 0 (LP) = 3
- Electron Geometry: Trigonal Planar
- Molecular Geometry: Trigonal Planar
- Planarity: Yes
Boron Trichloride ($BCl_3$)
- Central Atom: Boron (B)
- Valence electrons of B: 3
- Bonding Pairs (BP) with Chlorine (Cl): 3
- Lone Pairs (LP): (3 valence electrons - 3 bonding pairs * 2 electrons/pair) / 2 = 0 / 2 = 0
- Steric Number (SN): 3 (BP) + 0 (LP) = 3
- Electron Geometry: Trigonal Planar
- Molecular Geometry: Trigonal Planar
- Planarity: Yes
Phosphorus Trichloride ($PCl_3$)
- Central Atom: Phosphorus (P)
- Valence electrons of P: 5
- Bonding Pairs (BP) with Chlorine (Cl): 3
- Lone Pairs (LP): (5 valence electrons - 3 bonding pairs * 2 electrons/pair) / 2 = 2 / 2 = 1
- Steric Number (SN): 3 (BP) + 1 (LP) = 4
- Electron Geometry: Tetrahedral
- Molecular Geometry: Trigonal Pyramidal
- Planarity: No
Nitrogen Trichloride ($NCl_3$)
- Central Atom: Nitrogen (N)
- Valence electrons of N: 5
- Bonding Pairs (BP) with Chlorine (Cl): 3
- Lone Pairs (LP): (5 valence electrons - 3 bonding pairs * 2 electrons/pair) / 2 = 2 / 2 = 1
- Steric Number (SN): 3 (BP) + 1 (LP) = 4
- Electron Geometry: Tetrahedral
- Molecular Geometry: Trigonal Pyramidal
- Planarity: No
Xenon Hexafluoride ($XeF_6$)
- Central Atom: Xenon (Xe)
- Valence electrons of Xe: 8
- Bonding Pairs (BP) with Fluorine (F): 6
- Lone Pairs (LP): (8 valence electrons - 6 bonding pairs * 2 electrons/pair) / 2 = 2 / 2 = 1
- Steric Number (SN): 6 (BP) + 1 (LP) = 7
- Electron Geometry: Pentagonal Bipyramidal
- Molecular Geometry: Distorted Octahedral (due to lone pair influence)
- Planarity: No
Aluminium Trifluoride ($AlF_3$)
- Central Atom: Aluminium (Al)
- Valence electrons of Al: 3
- Bonding Pairs (BP) with Fluorine (F): 3
- Lone Pairs (LP): (3 valence electrons - 3 bonding pairs * 2 electrons/pair) / 2 = 0 / 2 = 0
- Steric Number (SN): 3 (BP) + 0 (LP) = 3
- Electron Geometry: Trigonal Planar
- Molecular Geometry: Trigonal Planar (in monomeric form)
- Planarity: Yes
Aluminium Trichloride ($AlCl_3$)
- Central Atom: Aluminium (Al)
- Valence electrons of Al: 3
- Bonding Pairs (BP) with Chlorine (Cl): 3
- Lone Pairs (LP): (3 valence electrons - 3 bonding pairs * 2 electrons/pair) / 2 = 0 / 2 = 0
- Steric Number (SN): 3 (BP) + 0 (LP) = 3
- Electron Geometry: Trigonal Planar
- Molecular Geometry: Trigonal Planar (in monomeric form)
- Planarity: Yes
Evaluating the Options for Planar Species
Now, let's check each option provided:
| Option | Species in Set | Planarity Status | Contains Only Planar Species? |
|---|---|---|---|
| 1 | $XeF_4$, $BF_3$, $PCl_3$ | Planar, Planar, Non-planar | No |
| 2 | $XeF_4$, $AlF_3$, $NCl_3$ | Planar, Planar, Non-planar | No |
| 3 | $XeF_6$, $BF_3$, $AlCl_3$ | Non-planar, Planar, Planar | No |
| 4 | $XeF_4$, $BF_3$, $BCl_3$ | Planar, Planar, Planar | Yes |
Conclusion on Planar Species Set
Based on the VSEPR theory analysis, the set {$XeF_4$, $BF_3$, $BCl_3$} consists solely of planar species. $XeF_4$ exhibits a square planar geometry, while both $BF_3$ and $BCl_3$ display trigonal planar geometries. These shapes ensure all atoms lie within a single plane.
Important Questions from Chemistry (CUET PG) Mixed
- Which of the following atmospheric gas does not dissolve in water at standard temperature and pressure conditions?
- Which of the following physical processes is responsible for the blue color of the sky?
- Arrange the following coal types in the increasing order of their heat content (KJ/kg)
(A). Peat
(B). Lignite
(C). Anthracite
(D). Bituminous
(E) Sub-bituminous
Choose the correct answer from the options given below: - In which of the following layers of atmosphere, does the temperature decrease with the increase in height from the earth's surafce?
(A). Troposphere
(B). Mesosphere
(C). Thermosphere
(D). Stratosphere
Choose the correct answer from the options given below: Choose the correct statement from the following:
(A). Water has highest density at 4°C
(B). Freezing point of water is 0°C
(C) An Ice cube does not completely dip in water, rather floats on water in a glass.
(D). Addition of common salt reduces freezing point of water.
Choose the correct answer from the options given below:
