Coordination number (CN) = number of ligands attached to central metal atom
Oxidation state (OS) = charge on central metal atom
EAN (Effective Atomic Number) = Z - OS + 2 × CN
Magnetic moment (μ) = √(n(n+2)) Bohr magneton (BM)
μ = √(4S(S+1)) BM for sp∈-only magnetic moment
Crystal field splitting energy (Δ) = energy difference between e.g. and t2g orbitals
Δ = (Δₒ) × (ligand field strength)
Optical isomerism occurs when complex has no plane of symmetry, no center of symmetry, and no axis of symmetry
Geometrical isomerism occurs when complex has different arrangement of ligands ∈ space
Coordination isomerism occurs when complex has different coordination entities

🪤 The 5 Mistakes That Cost Marks

Not understanding the concept of EAN and its application
Not being able to calculate oxidation state of central metal atom
Not being able to determine coordination number of complex
Not being able to identify type of isomerism exhibited by complex
Not being able to calculate magnetic moment of complex

✏️ 3 Solved PYQs

Question 1: What is the coordination number of [Ni(CN)₄]²⁻? Step 1: Identify the central metal atom and ligands Step 2: Determine the number of ligands attached to central metal atom Step 3: Calculate the coordination number Answer: CN = 4
Question 2: What is the oxidation state of Fe ∈ [Fe(CN)₆]³⁻? Step 1: Identify the central metal atom and ligands Step 2: Determine the charge on the complex Step 3: Calculate the oxidation state of Fe Answer: OS = +3
Question 3: What is the magnetic moment of [Cu(H₂O)₆]²⁺? Step 1: Identify the central metal atom and ligands Step 2: Determine the oxidation state of Cu Step 3: Calculate the number of unpaired electrons Step 4: Calculate the magnetic moment Answer: μ = √(1(1+2)) = √3 BM

🧠 The One Thing Most Students Get Wrong

Most students get the concept of EAN wrong and are not able to apply it to calculate the stability of complex
EAN is the sum of the atomic number of the metal and twice the number of ligands attached to it
EAN is used to predict the stability of complex and to determine the oxidation state of the metal

👁️ Ayush's Note

To solve coordination compound problems, first identify the central metal atom and ligands
Then determine the coordination number, oxidation state, and EAN
Use the EAN to predict the stability of the complex
For JEE Advanced and NEET, practice solving problems on optical, geometrical, and coordination isomerism
Also practice calculating magnetic moment and crystal field splitting energy

🔁 Last 5 Minutes Box

Revision of key concepts: EAN, CN, OS, magnetic moment, crystal field splitting energy
Quick practice of solved PYQs and previous year questions
Focus on understanding the concept of isomerism and its application
Practice calculating magnetic moment and crystal field splitting energy
Revision of shortcuts and formulas for quick calculation

📝 Practice MCQs

1. What is the coordination number of [Co(NH₃)₆]³⁺?

A) 4

B) 6

C) 8

D) 10

Answer: B) 6

2. What is the oxidation state of Cr ∈ [Cr(H₂O)₆]³⁺?

A) +2

B) +3

C) +4

D) +5

Answer: B) +3

3. What is the magnetic moment of [Fe(H₂O)₆]³⁺?

A) √(3(3+2)) BM

B) √(5(5+2)) BM

C) √(1(1+2)) BM

D) √(2(2+2)) BM

Answer: B) √(5(5+2)) BM

4. Which of the following complexes exhibit optical isomerism?

A) [Co(NH₃)₄Cl₂]⁺

B) [Co(NH₃)₆]³⁺

C) [Cr(H₂O)₆]³⁺

D) [Ni(CN)₄]²⁻

Answer: A) [Co(NH₃)₄Cl₂]⁺

5. What is the crystal field splitting energy of [Ni(H₂O)₆]²⁺?

A) 10000 cm⁻¹

B) 20000 cm⁻¹

C) 30000 cm⁻¹

D) 40000 cm⁻¹

Answer: B) 20000 cm⁻¹

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This post was curated by Jules, Exam Compass Bot, and edited for accuracy by Ayush.

📚 Related Topics

Continue your revision with these related guides:

Coordination number (CN) = number of ligands attached to central metal atom
Oxidation state (OS) = charge on central metal atom
EAN (Effective Atomic Number) = Z - OS + 2 × CN
Magnetic moment (μ) = √(n(n+2)) Bohr magneton (BM)
μ = √(4S(S+1)) BM for sp∈-only magnetic moment
Crystal field splitting energy (Δ) = energy difference between e.g. and t2g orbitals
Δ = (Δₒ) × (ligand field strength)
Optical isomerism occurs when complex has no plane of symmetry, no center of symmetry, and no axis of symmetry
Geometrical isomerism occurs when complex has different arrangement of ligands ∈ space
Coordination isomerism occurs when complex has different coordination entities