Spectrochemical Series NEET 2026: Ligand Field Order

What is the correct answer to the spectrochemical series NEET 2026 question?

Option A is correct for the spectrochemical series NEET 2026 question: CO produces the greatest splitting, followed by NH₃, H₂O and Cl⁻. The task is to rank these ligands from greatest to least crystal-field splitting, opposite to the increasing direction of the reference series.

The source is NEET UG 2026, held on 21 June 2026, Code-50, Chemistry, Co-ordination Compounds. This question bank classifies it as medium difficulty, not an official NTA difficulty rating.

The supplied options are:

• A)

• B)

• C)

• D)

Both A and B have the correct endpoints. NH₃ is stronger-field than H₂O, which makes A correct.

How do you start with the increasing spectrochemical series?

Step 1: read the reference series from weaker field to stronger field. Ligand field strength concerns the splitting of a metal’s d orbitals. Greater splitting means a stronger ligand field in a comparable coordination environment.

The supplied solution uses the octahedral splitting parameter: ${\Delta }_0$

This denotes the splitting between the two sets of d orbitals in an octahedral field. No particular complex is specified or needed for this ordering question.

The supplied NCERT Class 12 Chemistry, Chapter 9 reference gives this increasing sequence, continued across two lines:

Here, ox²⁻ means oxalate, and en means ethylenediamine. Field strength increases from left to right; the question asks for the opposite direction.

Use this empirical series as the basis of the solution. Neither electronegativity nor ligand charge alone can replace the listed order.

How do you extract the four ligands and reverse their order?

Steps 2 and 3 give option A: retain the four required entries, then reverse them. Extraction must preserve each ligand’s position in the reference. Check the middle pair as carefully as the endpoints.

Step 2: extract in increasing order.

Check every adjacent comparison:

• H₂O is stronger-field than Cl⁻.
• NH₃ is stronger-field than H₂O.
• CO is stronger-field than NH₃.

Step 3: reverse for decreasing strength.

Correct answer: option A. CO must come first and Cl⁻ last, ruling out C and D. The NH₃–H₂O comparison distinguishes A from B.

No numerical splitting values or calculations are supplied or required. The answer follows from relative positions alone.

If a marking scheme awards four marks for A and deducts one mark for B, the score difference would be: $4-(-1)=5\text{ marks}$

This conditional calculation concerns scoring, not orbital splitting. It is not part of the chemical solution.

Why is option B wrong even though its endpoints are correct?

B reverses the water–ammonia comparison. Remembering only that CO is strong-field and Cl⁻ is weak-field leaves the middle pair unresolved. Those endpoints cannot establish the complete sequence.

Compare the options directly:

• A, correct:

• B, incorrect:

H₂O is called aqua, while NH₃ is called ammine. B incorrectly places water above ammonia in field strength, whereas the reference gives: ${\mathrm{H}}_2\mathrm{O}<\mathrm{N}{\mathrm{H}}_3$

The repair is specific: verify every adjacent pair against the same increasing series before reversing it. Checking only the first and last ligands misses B’s error.

Negative ligand charge alone does not make Cl⁻ stronger-field than neutral CO or NH₃. Charge and field strength are different properties; use the empirical order.

Which order keeps F⁻, ox²⁻, H₂O and en in increasing field strength?

Answer C preserves the reference order, so no reversal is needed. This and the following two questions are original practice questions, not additional NEET PYQs.

Original practice question 1: Which sequence places F⁻, ox²⁻, H₂O and en in increasing field strength?

• A)

• B)

• C)

• D)

Extracting these entries directly from the reference gives:

C is correct. Stop after extraction because the practice stem already asks for increasing strength. Reversing automatically would turn the correct extraction into the wrong answer.

How do SCN⁻ and NCS⁻ differ in the spectrochemical series?

SCN⁻ comes before NCS⁻, and both come before NH₃ in the supplied increasing series. SCN⁻ denotes sulfur coordination, while NCS⁻ denotes nitrogen coordination. These are different donor-atom attachment modes of an ambidentate ligand, not interchangeable entries.

Original practice question 2: What is the increasing field-strength order of SCN⁻, NCS⁻ and NH₃?

Answer B follows by preserving the reference positions: $\mathrm{S}\mathrm{C}{\mathrm{N}}^{-}<\mathrm{N}\mathrm{C}{\mathrm{S}}^{-}<\mathrm{N}{\mathrm{H}}_3$

Copy ligand notation exactly during extraction. Matching elemental composition does not establish identical field strength when the donor atom differs. Extraction already gives the requested increasing order, so no reversal is needed.

Which ligand gives the largest octahedral splitting under comparable conditions?

Based on the reference series, CN⁻ is expected to give the greatest splitting among these choices, making D correct. The comparison holds the metal ion, oxidation state and coordination geometry constant.

Original practice question 3: Which ligand is expected to produce the greatest octahedral splitting under those conditions?

Extract the relevant order:

CN⁻ is rightmost in the increasing series, indicating the largest splitting under the stated comparable conditions. For your next ordering question: identify the requested direction, extract the relevant ligands, then check every adjacent comparison.

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Keep going with Conductors in Electrostatics NEET 2026: Option C Explained.