Summary: Understand electronic configurations, oxidation states, crystal field splitting, magnetic moments and isomerism, since these can be worked out. Memorise colours, specific compound properties, the preparation and reactions of K2Cr2O7 and KMnO4, and the list of ligand names. Coordination compounds in particular is a chapter where understanding pays well.Two different kinds of chapter
Students often put the d- and f-block and coordination compounds together under "Inorganic, to be memorised". That is half right. The d-block chapter is largely about trends and a few important compounds, while coordination compounds is closer to a reasoning chapter, with naming rules, isomer counting and crystal field theory that behave like small puzzles.
The JEE Main 2026 syllabus supports this reading. For the d-block it lists general trends of the first-row transition elements (ionisation enthalpy, oxidation states, radii, colour, catalytic and magnetic behaviour, complex formation, interstitial compounds, alloys), the preparation, properties and uses of K2Cr2O7 and KMnO4, and the lanthanoid contraction. For coordination compounds it lists Werner's theory, ligands, coordination number, denticity and chelation, IUPAC naming of mononuclear complexes, isomerism, valence bond theory, basic crystal field theory, colour and magnetic properties, and the uses of complexes. Our wider Inorganic Chemistry plan shows where these chapters fit among the rest.
The split
| Understand and derive | Memorise |
|---|---|
| Electronic configurations of first-row transition elements and their ions, including Cr and Cu exceptions | Common colours of transition metal ions and compounds |
| Why oxidation states vary, and which are most stable | Preparation and key reactions of K2Cr2O7 and KMnO4, with balanced equations |
| Magnetic moment from unpaired electrons, μ = √(n(n+2)) BM | Names and abbreviations of common ligands (en, ox, EDTA and others) |
| Trends in radii, including lanthanoid contraction and its effect on 4d and 5d elements | Uses of complexes named in NCERT (in qualitative analysis, metal extraction, biology) |
| IUPAC naming rules for complexes | Examples of catalysts and alloys given in NCERT |
| Geometrical and optical isomer counting | Common oxidation states of lanthanoids and actinoids |
| Crystal field splitting in octahedral and tetrahedral fields; high spin and low spin | The spectrochemical series, in order |
The spectrochemical series is the one memorised item that opens up most of the understanding column. Learn it early. A common version, from weak to strong field, runs I− < Br− < Cl− < F− < OH− < H2O < NH3 < en < CN− < CO. NCERT gives a fuller version; use the one in your NCERT book.
Worked example: two iron(III) complexes
Compare [Fe(CN)6]3− and [FeF6]3−: number of unpaired electrons, spin-only magnetic moment and type of hybridisation in valence bond terms.
Step 1: oxidation state and d count. In both, iron is +3. Fe is [Ar]3d64s2, so Fe3+ is 3d5.
Step 2: field strength. CN− is a strong field ligand, F− a weak one.
Step 3: filling. In [Fe(CN)6]3−, the large splitting pairs the electrons in the lower t2g set: t2g5, one unpaired electron. In [FeF6]3−, the small splitting leaves all five unpaired: t2g3eg2.
Step 4: magnetic moment. For n = 1, μ = √3 ≈ 1.73 BM. For n = 5, μ = √35 ≈ 5.92 BM.
Step 5: valence bond picture. The cyanide complex uses inner d orbitals, d2sp3 (inner orbital, low spin). The fluoride complex uses outer d orbitals, sp3d2 (outer orbital, high spin).
Nothing here was memorised except the position of two ligands in the series. The same five steps handle almost every magnetic moment question in this chapter.
Naming and isomers, briefly
K3[Fe(C2O4)3] is potassium trioxalatoferrate(III): ligands in alphabetical order, then the metal with "-ate" because the complex ion is negative, then the oxidation state. Work through the NCERT naming rules once with ten examples and they stay with you.
For isomers, [Co(NH3)4Cl2]+ has two geometrical isomers, cis and trans. [Co(en)3]3+ has no geometrical isomers but exists as a pair of optical isomers. Draw the octahedron every time rather than trying to recall answers.
How to memorise the d-block facts
- Write the preparation of K2Cr2O7 from chromite ore and of KMnO4 from pyrolusite as step-by-step flow charts, then rewrite them from memory twice a week for three weeks.
- For oxidising reactions of KMnO4 and K2Cr2O7, learn the half-reactions in acidic medium. Most full equations follow by balancing electrons.
- Make a single-page colour table of ions and compounds from NCERT. Read it the night before every Chemistry test.
- For the f-block, keep to what the syllabus names: configurations, oxidation states and lanthanoid contraction.
A two-week plan
| Days | Work |
|---|---|
| 1 to 3 | d-block: configurations, trends, oxidation states, magnetic moment. NCERT line by line. |
| 4 to 5 | K2Cr2O7, KMnO4, f-block. Flow charts and half-reactions. |
| 6 to 7 | Coordination: Werner's theory, ligands, denticity, IUPAC naming. Name 20 complexes. |
| 8 to 9 | Isomerism with drawings. Count isomers for 15 complexes. |
| 10 to 12 | Valence bond theory and crystal field theory. 25 magnetic moment and colour questions. |
| 13 to 14 | Previous year questions from both chapters, then a timed test. |
Our notes on d- and f-block elements and coordination compounds follow NCERT closely, and the previous year papers section lets you practise real questions.
Common questions
Is NCERT enough for coordination compounds?
For theory, yes. For practice, you need a larger set of isomer counting and magnetic moment questions than NCERT gives, from a module or question bank.
Do I need crystal field theory in depth?
The JEE Main syllabus asks for basic ideas of crystal field theory with colour and magnetic properties. Octahedral and tetrahedral splitting, high and low spin, and simple colour reasoning cover it.
How do I remember colours?
Keep one table, read it often, and link colours to d-electron count where you can. A few, like colourless Sc3+ and Zn2+, follow directly from an empty (d0) or completely filled (d10) d subshell, which allows no d-d transition.