Is d And f Block Elements & Coordination Compounds part of the EAPCET Chemistry syllabus?

Yes. d And f Block Elements & Coordination Compounds is taught in Intermediate second year Chemistry, and the EAPCET Engineering syllabus is based on the Intermediate first- and second-year syllabus. Check the official notification each year for any changes.

How many Chemistry questions are there in EAPCET?

40 of the 160 questions in the Engineering paper are Chemistry, spread across 24 chapters.

What mistakes do students make in d And f Block Elements & Coordination Compounds?

Removing 3d electrons before 4s when forming ions — 4s electrons leave first, so Fe³⁺ is 3d⁵, not 3d³4s². Ignoring the ligand field when counting unpaired electrons — the same Fe³⁺ gives 1 unpaired electron with CN⁻ but 5 with F⁻. Forgetting the -ate ending for anionic complexes — K₄[Fe(CN)₆] is potassium hexacyanidoferrate(II), not hexacyanidoiron(II). Treating zinc as a typical transition metal — Zn²⁺ is d¹⁰, so its compounds are colourless and diamagnetic.

EAPCET Chemistry · Intermediate second year

d And f Block Elements & Coordination Compounds

This chapter covers transition and inner-transition elements, and coordination compounds: their naming, bonding, isomerism and magnetic properties.

Subject: Chemistry
Taught in: Intermediate second year
Chemistry in the paper: 40 of 160 questions

Key formulas and results

Transition metals show variable oxidation states and form coloured ions
Spin-only magnetic moment $\mu = \sqrt{n(n + 2)}$ BM, where $n$ is the number of unpaired electrons
Lanthanoid contraction makes 4d and 5d elements of a group similar in size
Strong-field ligands such as CN⁻ and CO pair electrons; weak-field ligands such as halides do not
Potassium permanganate and potassium dichromate are strong oxidising agents
Effective atomic number: $\text{EAN} = Z \text{ of metal} - \text{oxidation state} + 2 \times \text{coordination number}$
Octahedral crystal field stabilisation energy: $\text{CFSE} = (-0.4\,n_{t_{2g}} + 0.6\,n_{e_g})\,\Delta_o$ , plus pairing energy for each extra pair
Tetrahedral splitting: $\Delta_t = \frac{4}{9}\Delta_o$ , so tetrahedral complexes are almost always high spin
Spin-only magnetic moments: $n = 1, 2, 3, 4, 5$ unpaired electrons $\to \mu = 1.73, 2.83, 3.87, 4.90, 5.92$ BM
Hybridisation and shape: sp³ tetrahedral; dsp² square planar; sp³d or dsp³ trigonal bipyramidal; d²sp³ (inner orbital) and sp³d² (outer orbital) octahedral
Crystal field splitting $\Delta_o$ increases 3d < 4d < 5d (about 50% from 3d to 4d and about 25% from 4d to 5d) and increases with the oxidation state of the metal
Werner’s theory: primary valency = oxidation state (ionisable, satisfied by anions); secondary valency = coordination number (non-ionisable, directional)
Geometrical isomers of octahedral complexes: $\ce{MA4B2} = 2$ (cis, trans); $\ce{MA3B3} = 2$ (fac, mer); $\ce{MA3B2C} = 3$ ; square planar $\ce{MABCD} = 3$

What this chapter covers

General properties of transition elements
Lanthanoid contraction
KMnO₄ and K₂Cr₂O₇
Werner’s theory and IUPAC naming
Valence bond and crystal field theory
Isomerism in complexes

How it is usually asked

Magnetic moment
IUPAC name of a complex
Hybridisation and geometry
Number of isomers

Understanding d And f Block Elements & Coordination Compounds

Transition elements have partly filled d orbitals in the atom or in a common ion. Because the (n − 1)d and ns energies are close, they show variable oxidation states (manganese reaches +7), form coloured ions through d–d transitions, are often paramagnetic, make good catalysts and form complexes. Zn, Cd and Hg have full d¹⁰ configurations in all states and are not typical transition metals. Lanthanoid contraction, caused by poor shielding by 4f electrons, makes Zr and Hf almost the same size.

In a coordination compound, a central metal ion is bonded to ligands that donate lone pairs. IUPAC naming lists ligands alphabetically before the metal, gives the oxidation state in Roman numerals, and adds “-ate” to the metal for an anionic complex (ferrate, cuprate, argentate). Isomerism includes geometrical (cis/trans), optical, ionisation, linkage and hydrate isomers. The coordination number and geometry decide which isomers are possible.

Crystal field theory explains colour and magnetism. In an octahedral field the d orbitals split into lower t₂g and higher e_g sets. Strong-field ligands such as CN⁻ and CO cause a large split, so electrons pair in t₂g (low spin); weak-field ligands such as F⁻ and Cl⁻ give a small split and high spin. Count unpaired electrons, then use μ = √[n(n + 2)] BM. KMnO₄ and K₂Cr₂O₇ are important oxidising agents, especially in acid.

Worked example

EAPCET-style question

The spin-only magnetic moment of $\ce{[Fe(CN)6]^3-}$ is approximately:

(1)0 BM
(2)1.73 BM
(3)2.83 BM
(4)5.92 BM

Solution

Oxidation state of Fe: $x + 6(-1) = -3$ , so $x = +3$ .
Fe is $[\text{Ar}]\,3d^6 4s^2$ ; $\ce{Fe^3+}$ is $3d^5$ .
$\ce{CN-}$ is a strong-field ligand, so the five electrons pair up in $t_{2g}$ : $t_{2g}^5 e_g^0$ , leaving 1 unpaired electron ( $d^2sp^3$ , low spin).
$\mu = \sqrt{1(1 + 2)} = \sqrt{3} \approx 1.73$ BM.
5.92 BM would be the high-spin value seen with weak-field $\ce{F-}$ in $\ce{[FeF6]^3-}$ .

Answer: 1.73 BM

Shortcuts and results to remember

In sodium nitroprusside, $\ce{Na2[Fe(CN)5NO]}$ , iron is in the +2 state and the nitrosyl ligand is $\ce{NO+}$ .
For coordination number 4, tetrahedral (sp³) complexes show no geometrical isomerism and square planar (dsp²) complexes show no optical isomerism; Pd(II) and Pt(II) complexes are square planar.
$\ce{[Ni(CO)4]}$ is tetrahedral and diamagnetic, $\ce{[NiCl4]^2-}$ is tetrahedral and paramagnetic, and $\ce{[Ni(CN)4]^2-}$ is square planar and diamagnetic.
Mond process purifies nickel through volatile $\ce{Ni(CO)4}$ , van Arkel process purifies Zr and Ti, EDTA titration estimates water hardness ( $\ce{Ca^2+}$ , $\ce{Mg^2+}$ ), and dimethylglyoxime detects $\ce{Ni^2+}$ .
$\ce{KMnO4}$ has Mn in +7 (d⁰) yet is deeply coloured because of charge transfer, not d–d transitions; d⁰ and d¹⁰ ions such as $\ce{Ti^4+}$ and $\ce{Zn^2+}$ are otherwise colourless.
Chelating ligands such as en, ox²⁻ and hexadentate EDTA⁴⁻ give more stable complexes than similar monodentate ligands (chelate effect, an entropy gain).

Common mistakes to avoid

Removing 3d electrons before 4s when forming ions — 4s electrons leave first, so Fe³⁺ is 3d⁵, not 3d³4s².
Ignoring the ligand field when counting unpaired electrons — the same Fe³⁺ gives 1 unpaired electron with CN⁻ but 5 with F⁻.
Forgetting the -ate ending for anionic complexes — K₄[Fe(CN)₆] is potassium hexacyanidoferrate(II), not hexacyanidoiron(II).
Treating zinc as a typical transition metal — Zn²⁺ is d¹⁰, so its compounds are colourless and diamagnetic.

How to prepare it

Learn the spectrochemical series of ligands — it settles most hybridisation and magnetism questions.

Once the formulas feel familiar, test them the way the exam does: practise d And f Block Elements & Coordination Compounds questions chapter-wise, then attempt a full previous year paper to see whether it holds up under a 3-hour timer.

Related Chemistry chapters

See every chapter in the EAPCET Chemistry syllabus.

Practise d And f Block Elements & Coordination Compounds chapter-wise

Chapter-wise quizzes show exactly which topics in this chapter you still get wrong — before a full paper does.

Frequently asked questions

Is d And f Block Elements & Coordination Compounds part of the EAPCET Chemistry syllabus?: Yes. d And f Block Elements & Coordination Compounds is taught in Intermediate second year Chemistry, and the EAPCET Engineering syllabus is based on the Intermediate first- and second-year syllabus. Check the official notification each year for any changes.
How should I prepare d And f Block Elements & Coordination Compounds for EAPCET?: Learn the spectrochemical series of ligands — it settles most hybridisation and magnetism questions.
How many Chemistry questions are there in EAPCET?: 40 of the 160 questions in the Engineering paper are Chemistry, spread across 24 chapters.
What mistakes do students make in d And f Block Elements & Coordination Compounds?: Removing 3d electrons before 4s when forming ions — 4s electrons leave first, so Fe³⁺ is 3d⁵, not 3d³4s². Ignoring the ligand field when counting unpaired electrons — the same Fe³⁺ gives 1 unpaired electron with CN⁻ but 5 with F⁻. Forgetting the -ate ending for anionic complexes — K₄[Fe(CN)₆] is potassium hexacyanidoferrate(II), not hexacyanidoiron(II). Treating zinc as a typical transition metal — Zn²⁺ is d¹⁰, so its compounds are colourless and diamagnetic.