Coordination Compounds

Chemistry · Class 12

Simulation · Chemistry · Class 12

Which orbitals does the metal use: inner d or outer d?

"Which orbitals does the metal use: inner d or outer d?" is a free, interactive Class 12 Chemistry simulation for NEET and JEE, built on the NCERT section "Valence bond theory" in Coordination Compounds. Orbital boxes 3d, 4s, 4p, 4d for the metal ion; the ligand either forces pairing (freeing inner d orbitals, d²sp³ or dsp²) or not (sp³d² or sp³), giving geometry and unpaired electrons. NEET has asked about this idea 4 times in 10 years of papers. JEE Main asked 80 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).

From the lesson Valence bond theory in Coordination Compounds. Change the values and watch what happens.

Which orbitals does the metal use: inner d or outer d?Chemistry · Class 12

What it shows

NCERT §5.5.1; §5.5.2

Orbital boxes 3d, 4s, 4p, 4d for the metal ion; the ligand either forces pairing (freeing inner d orbitals, d²sp³ or dsp²) or not (sp³d² or sp³), giving geometry and unpaired electrons.

Controls

3 to try

  • Selectcomplex [NiCl₄]²⁻ / [Ni(CN)₄]²⁻ / [Ni(CO)₄] / [Co(NH₃)₆]³⁺ / [CoF₆]³⁻ / [Fe(CN)₆]³⁻ / [FeF₆]³⁻
  • Togglepair electrons first (strong ligand) / don't
  • Readoutshybridisation, inner/outer orbital, geometry, unpaired, μ (BM)

Try this

Make Ni²⁺ square planar and diamagnetic, then make it tetrahedral with μ = 2.83 BM.

Common mistake

[NiCl₄]²⁻ and [Ni(CO)₄] are both paramagnetic because both are tetrahedral.

In NEET

10 years of papers

Asked 4 times in 10 years of NEET.

See the past questions: Crystal Field Theory, Coordination Compounds, Coordination Compounds (chapter)

In JEE Main

42 shifts analysed

80 questions from Coordination Compounds across the 42 JEE Main shifts Lumi has analysed (2017–2026).

See the past questions

The idea behind it

NCERT §5.5.1

  • Werner's theory could not explain why only some elements form complexes, why the bonds are directional, or where the magnetic and optical properties come from. VBT and CFT are the two models treated at this level.
  • In VBT the metal mixes (n−1)d, ns, np orbitals, or ns, np, nd orbitals, to make a set of identical hybrid orbitals pointing in fixed directions. Each hybrid orbital accepts an electron pair from a ligand.
  • Hybridisation and shape: CN 4, sp³ tetrahedral; CN 4, dsp² square planar; CN 5, sp³d trigonal bipyramidal; CN 6, sp³d² or d²sp³ octahedral.
  • [Co(NH₃)₆]³⁺: Co³⁺ is 3d⁶. The six electrons pair into three 3d orbitals, leaving two inner 3d orbitals for d²sp³ hybridisation. No electron is unpaired, so the octahedral complex is diamagnetic: an inner orbital, low spin or spin paired complex.
  • [CoF₆]³⁻ uses the outer 4d orbitals (sp³d²), keeps four unpaired electrons and is paramagnetic: an outer orbital, high spin or spin free complex.
  • [NiCl₄]²⁻: Ni²⁺ is 3d⁸, the four Cl⁻ pairs go into sp³ hybrids, the complex is tetrahedral and two unpaired electrons make it paramagnetic. [Ni(CO)₄] is also tetrahedral but diamagnetic, because nickel is at zero oxidation state with no unpaired electron.
  • [Ni(CN)₄]²⁻: the 3d⁸ electrons pair up to free one 3d orbital, giving dsp² hybrids. The complex is square planar and diamagnetic.
  • Hybrid orbitals are not real objects; hybridisation is a mathematical treatment of the atomic wave functions.
  • Magnetic data often reveal the geometry in VBT: a paramagnetic four-coordinate Ni²⁺ complex is tetrahedral, while a diamagnetic one is square planar.

Questions

5 answers

What does the "Which orbitals does the metal use: inner d or outer d?" simulation show?
Orbital boxes 3d, 4s, 4p, 4d for the metal ion; the ligand either forces pairing (freeing inner d orbitals, d²sp³ or dsp²) or not (sp³d² or sp³), giving geometry and unpaired electrons.
What mistake does the "Which orbitals does the metal use: inner d or outer d?" simulation fix?
A common mistake it clears up: [NiCl₄]²⁻ and [Ni(CO)₄] are both paramagnetic because both are tetrahedral.
Has NEET asked about this idea?
Yes. NEET has asked about this idea 4 times in 10 years of papers.
Does JEE Main ask questions from Coordination Compounds?
Yes. JEE Main asked 80 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
Is this simulation free?
Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "Valence bond theory" in Coordination Compounds (Class 12 Chemistry).

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