Q.75 Chemistry ⭐ 360° Option Elimination Active

NEET 2026 Chemistry Question 75 Solution

Topic: Chemical Bonding and Molecular Structure & Coordination Compounds · Official NTA Booklet Code 50

Question

Match the species in List I with their geometry in List II. List I: A. PCl₅; B. BrF₅; C. BF₄⁻; D. [Ni(CN)₄]²⁻. List II: I. Tetrahedral; II. Square Planar; III. Trigonal bipyramidal; IV. Square pyramidal. Choose the correct answer from the options given below:

✓

Verified Against NTA Final Answer Key

Option (2) : A-III, B-IV, C-I, D-II

📚 Chemical Bonding and Molecular Structure & Coordination Compounds Easy

📋 Given Parameters & Problem Setup

Species A PCl₅

Species B BrF₅

Species C BF₄⁻

Species D [Ni(CN)₄]²⁻

Geometries I. Tetrahedral, II. Square Planar, III. Trigonal bipyramidal, IV. Square pyramidal

⚡

The 30-Second Exam Hall Shortcut: ⚡ Steric Number & Electron Pair Fingerprint

⏱️ Save ~50 seconds

Match PCl₅ (5 bp = TBP) and [Ni(CN)₄]²⁻ (d⁸ strong field = Square Planar) to finish in 10 seconds!

1 A. PCl₅: 5 bond pairs, 0 lone pairs -> Steric Number 5 -> Trigonal bipyramidal (III) -> A-III.

2 This immediately eliminates Option (1)!

3 D. [Ni(CN)₄]²⁻: Ni²⁺ (3d⁸) with strong field CN⁻ forces pairing -> dsp² hybridization -> Square Planar (II) -> D-II.

4 This eliminates Option (3) and Option (4)!

5 Confirm B and C: BrF₅ (5 bp + 1 lp = Square pyramidal, IV); BF₄⁻ (4 bp + 0 lp = Tetrahedral, I).

6 Option (2) is rock-solid: A-III, B-IV, C-I, D-II!

🛡️

Why You Can 100% Trust This Shortcut: Direct application of VSEPR theory for main group species and Crystal Field / Valence Bond Theory for coordination complexes.

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Determine Geometry of PCl₅ (Species A)

Phosphorus has 5 valence electrons, all forming single σ bonds with five chlorine atoms. Steric number = 5 (5 bond pairs + 0 lone pairs). Hybridization = sp³d.

\text{Steric Number} = 5 + 0 = 5 \implies \text{Trigonal bipyramidal (III)}

• Match: A -> III.

Step 2

Determine Geometry of BrF₅ (Species B)

Bromine has 7 valence electrons: 5 form single bonds with fluorine, leaving 1 lone pair. Steric number = 5 bond pairs + 1 lone pair = 6. Hybridization = sp³d² with octahedral electron geometry and square pyramidal molecular shape.

\text{Steric Number} = 5 + 1 = 6 \implies \text{Square pyramidal (IV)}

• Match: B -> IV.

Step 3

Determine Geometry of BF₄⁻ (Species C)

Boron has 3 valence electrons + 1 negative charge = 4 electrons, forming four σ bonds with four fluorine atoms. Steric number = 4 bond pairs + 0 lone pairs = 4. Hybridization = sp³.

\text{Steric Number} = 4 + 0 = 4 \implies \text{Tetrahedral (I)}

• Match: C -> I.

Step 4

Determine Geometry of [Ni(CN)₄]²⁻ (Species D)

Nickel is in the +2 oxidation state (3d⁸). Cyanide (CN⁻) is a strong field ligand that forces the 3d electrons to pair up, leaving one vacant 3d orbital. Hybridization is dsp² with a square planar geometry.

\text{Ni}^{2+} (3d^8) + 4\text{CN}^- \xrightarrow{\text{pairing}} dsp^2 \implies \text{Square Planar (II)}

• Match: D -> II.
• Full Match: A-III, B-IV, C-I, D-II (Option 2).

⭐

360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 A

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Swaps geometries of PCl₅ and BrF₅.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing 5 bond pairs with 5 bond pairs + 1 lone pair.

2 B

✓ 100% Correct

Verdict & Scientific Reason:

Exact match: PCl₅ is TBP (III), BrF₅ is square pyramidal (IV), BF₄⁻ is tetrahedral (I), and [Ni(CN)₄]²⁻ is square planar (II).

💡

Why this is airtight: None; flawless VSEPR and CFT alignment.

3 C

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Assigns tetrahedral to BrF₅ and square pyramidal to [Ni(CN)₄]²⁻.

⚠️

Student Fallacy (Why candidates pick this trap): Miscounting electron pairs.

4 D

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Assigns square planar to BrF₅.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing square planar (AX₄E₂) with square pyramidal (AX₅E).

⚠️

NTA Trap Alert: Confusing BrF₅ (Square Pyramidal) with PCl₅ (TBP)

Both PCl₅ and BrF₅ have five peripheral halogen atoms, but PCl₅ has NO lone pairs (Trigonal bipyramidal), while BrF₅ has ONE lone pair on bromine (Square pyramidal).

🛡️ How to avoid the -1 mark: Count total valence electrons: PCl₅ has 5 pairs (TBP); BrF₅ has 6 pairs (Square pyramidal).

📖

Core NEET Syllabus Standard

NEET Chemistry Core Syllabus · Chemical Bonding and Coordination Compounds Standard Benchmark

Core Scientific Principle Tested:

"Shape is dictated by steric number and lone pairs: 5+0 = TBP, 5+1 = square pyramidal, 4+0 = tetrahedral, dsp² = square planar."

Syllabus Focus: VSEPR Theory shapes and dsp² square planar coordination geometries

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

PCl₅ = TBP; BrF₅ = Square Pyramid; BF₄⁻ = Tetrahedral; [Ni(CN)₄]²⁻ = Square Planar!

Ready to attempt under real exam pressure?

Test your speed and accuracy in the authentic 180-minute timed NTA simulator.

Launch NEET 2026 CBT Test →

← Previous (Q.74) All Chemistry Questions Grid Next (Q.76) →

Spotted a mistake in this solution? Report an error (support@mycompetitiveexams.com)

⚖️ Legal & Fair Dealing Notice: Sourced from publicly released NEET 2026 question papers and NEET answer keys for private study, research, and non-commercial educational practice under Fair Dealing (Section 52(1)(a) of the Indian Copyright Act, 1957). Not affiliated with or endorsed by NTA or NMC.

NEET 2026 Chemistry Question 75 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Steric Number & Electron Pair Fingerprint

Step-by-Step Rigorous Workflow & Mathematical Proof

Determine Geometry of PCl₅ (Species A)

Determine Geometry of BrF₅ (Species B)

Determine Geometry of BF₄⁻ (Species C)

Determine Geometry of [Ni(CN)₄]²⁻ (Species D)

360° Option Elimination Engine Key Feature

NTA Trap Alert: Confusing BrF₅ (Square Pyramidal) with PCl₅ (TBP)

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

🔗 Related Questions — Coordination Compounds

Systematic Group Classification in Qualitative Salt Analysis

Paramagnetism vs. Diamagnetism in Nickel Complexes

Correct Order of Wavelength of Light Absorbed by Coordination Complexes

Minimum Conductance in Aqueous Solution of Cobalt Ammine Complexes

Solve 4 NEET Questions a Day — One per Subject