JEE Chemistry — Inorganic Chemistry Complete Chapter Guide

Chapter Overview & Weightage

Inorganic Chemistry is the single largest chunk of JEE Chemistry — typically 7-8 questions in JEE Main and 2-3 questions in JEE Advanced. That’s roughly 28-32 marks in Main alone. Students who crack this chapter well have a massive scoring advantage because the questions are mostly factual or application-based, not calculation-heavy.

JEE Main 2024 consistently gave 7 questions from Inorganic Chemistry across both shifts. Coordination Compounds alone contributed 2 questions in JEE Main 2024 Shift 2 (Jan session). d-Block and Coordination Compounds together are the highest-weightage subtopics.

Year	JEE Main (Questions)	JEE Advanced (Marks)	Hottest Subtopic
2024	7–8	6–8	Coordination Compounds
2023	7	5–6	p-Block (Group 16/17)
2022	8	7	d-Block + Coordination
2021	7	6	Metallurgy + p-Block
2020	7	5	Coordination Compounds
2019	6–7	6	s-Block + p-Block

The pattern is clear: Coordination Compounds and d-Block are the spine of Inorganic for JEE. p-Block (Groups 15, 16, 17, 18) is the next priority. Metallurgy appears predictably in 1-2 questions per paper.

Key Concepts You Must Know

Ranked by exam frequency — handle these in order:

Tier 1 — Non-negotiable (appear almost every year)

CFSE (Crystal Field Stabilisation Energy) — octahedral vs tetrahedral field, calculation for d⁰ to d¹⁰ configurations
EAN rule and exceptions — when 18-electron rule holds, when it breaks (Fe complexes)
Colour of coordination compounds — d-d transitions, which complexes are colourless and why
VBT vs CFT — inner orbital vs outer orbital complexes, sp³, dsp², d²sp³ hybridisation
p-Block anomalies — why N₂ is less reactive than P₄, why F is a stronger oxidising agent than Cl despite lower bond energy
Oxidation states in d-Block — which element shows the highest and most stable oxidation states, and the trend
Extraction processes — froth flotation, roasting, smelting, electrolytic refining; which ore uses which method

Tier 2 — High probability (appear most years)

Periodic trends: ionisation enthalpy exceptions (Be > B, N > O, Mg > Al), electron gain enthalpy anomalies
Structures of oxoacids — H₂SO₄, HNO₃, H₃PO₄, HClO₄ (number of lone pairs, π bonds, oxidation state)
Isomerism in coordination compounds — ionisation, linkage, geometrical, optical (know examples for each)
Magnus salt, Zeise’s salt — classic examples for pi complexes
Interhalogen compounds — types IF₃, IF₅, IF₇, their shapes

Tier 3 — Cover if you have time

Diagonal relationship (Li-Mg, Be-Al, B-Si)
Anomalous behaviour of Li, Be, B
Cement, glass, plaster of paris compositions
f-Block — lanthanoid contraction and its consequences

Important Formulas

Octahedral field:

\text{CFSE} = (-0.4x + 0.6y) \cdot \Delta_o

where $x$ = number of electrons in $t_{2g}$ , $y$ = number of electrons in $e_g$

Tetrahedral field:

\Delta_t = \frac{4}{9}\Delta_o

CFSE (tet) uses $+0.6$ for $e$ orbitals and $-0.4$ for $t_2$ orbitals (note: labelling flips in tetrahedral)

\mu = \sqrt{n(n+2)} \text{ BM}

where $n$ = number of unpaired electrons. Use this to back-calculate the number of unpaired electrons from a given $\mu$ value — a very common JEE question type.

\text{EAN} = Z - \text{oxidation state} + 2 \times \text{(number of ligands)}

Noble gas configuration = 36 (Kr), 54 (Xe), or 86 (Rn). When EAN = 36, the complex obeys the 18-electron rule.

When to use CFSE formula: Any question asking whether a complex is high spin or low spin, whether it’s coloured, or its magnetic moment. If the question gives $\Delta_o$ and pairing energy $P$ , compare: $\Delta_o > P$ → low spin (strong field), $\Delta_o < P$ → high spin (weak field).

When to use magnetic moment formula: Questions like “a complex of Cr³⁺ has a magnetic moment of 3.87 BM — identify the hybridisation.” Work backwards: $n = 3$ , that’s 3 unpaired electrons, matches d³ configuration of Cr³⁺, hybridisation is $d^2sp^3$ .

Solved Previous Year Questions

PYQ 1 — JEE Main 2024, January Shift 1

Question: The IUPAC name of $[\text{Pt}(\text{NH}_3)_2\text{Cl}_2]$ is:

(A) Diamminedichloroplatinum(II) (B) Dichlorodiamminoplatinum(II) (C) Platinum(II) diamminedichloride (D) Diamminedichloridoplatinum(II)

Solution:

The correct IUPAC name uses the 2005 IUPAC recommendations — ligands are named in alphabetical order (ignoring multiplying prefixes), and the oxidation state of the metal comes at the end in Roman numerals within parentheses.

Ligands: ammine (NH₃) and chlorido (Cl⁻). Alphabetically: “a” for ammine comes before “c” for chlorido.

\text{diamminedichloridoplatinum(II)}

Answer: (D)

The old convention wrote “chloro” but current IUPAC (2005) uses “chlorido” for anionic ligands. JEE has started testing this distinction — always use the -ido suffix for anionic ligands: chlorido, bromido, cyanido.

PYQ 2 — JEE Main 2023, April Shift 2

Question: Among the following, the complex that is diamagnetic is:

(A) $[\text{CoF}_6]^{3-}$ (B) $[\text{Fe}(\text{CN})_6]^{3-}$ (C) $[\text{Ni}(\text{CO})_4]$ (D) $[\text{MnCl}_4]^{2-}$

Solution:

Diamagnetic means zero unpaired electrons.

$[\text{CoF}_6]^{3-}$ : Co³⁺ is d⁶, F⁻ is a weak field ligand → high spin → 4 unpaired electrons. Paramagnetic.
$[\text{Fe}(\text{CN})_6]^{3-}$ : Fe³⁺ is d⁵, CN⁻ is a strong field ligand → low spin → 1 unpaired electron. Still paramagnetic.
$[\text{Ni}(\text{CO})_4]$ : Ni is d¹⁰ here. CO is a strong field ligand, so the complex uses sp³ hybridisation. d¹⁰ means all electrons paired. Diamagnetic.
$[\text{MnCl}_4]^{2-}$ : Mn²⁺ is d⁵, Cl⁻ is weak field → 5 unpaired electrons. Paramagnetic.

Answer: (C)

Ni(CO)₄ is a textbook example. CO forces all d electrons to pair up. Remember that Ni is d¹⁰ in its zero oxidation state here — don’t mistakenly assign Ni²⁺ configuration.

PYQ 3 — JEE Main 2022, June Shift 1

Question: The correct order of first ionisation enthalpy is:

(A) Na < Mg < Al < Si (B) Na < Al < Mg < Si (C) Mg < Na < Al < Si (D) Al < Na < Mg < Si

Solution:

The general trend across a period is increasing IE₁. But two exceptions break the smooth curve:

Mg > Al: Mg has a fully filled 3s² subshell (extra stability). Al has one electron in 3p¹ — removing it is easier because 3p is higher in energy than 3s.
Na < Mg < Si is straightforward (increasing nuclear charge).
So the actual order: Na < Al < Mg < Si

Answer: (B)

The most common error here is writing Na < Mg < Al < Si by just following the “increases across period” trend without remembering the Mg-Al exception. This exception appears in almost every JEE paper in some form.

Difficulty Distribution

For JEE Main:

Difficulty	% of Questions	Description
Easy	40%	Direct recall — IUPAC names, oxidation states, common ore names, hybridisation from ligand count
Medium	45%	Application — CFSE calculation, identifying isomers, explaining trends with reasoning
Hard	15%	Multi-step — combining CFSE with magnetic moment, linking structure to property

For JEE Advanced, the distribution shifts: Easy ~20%, Medium ~50%, Hard ~30%. Advanced questions often combine two concepts — e.g., a coordination compound question that also tests oxidation state chemistry.

JEE Main Inorganic questions are among the fastest to solve in the paper. A student who has memorised properties of d-Block elements and Coordination Compound rules correctly can answer 5-6 Inorganic questions in under 8 minutes. This is your speed section.

Expert Strategy

Week 1 of Inorganic revision: Attack Coordination Compounds with full focus. Do IUPAC nomenclature, hybridisation and shape, isomerism (all 6 types with one example each), CFSE calculation, magnetic moment. This single subtopic can give you 2-3 marks on exam day.

Week 2: p-Block Groups 15, 16, 17. Don’t try to memorise everything — instead learn the pattern within each group: how does the structure of the oxoacid change as you go down the group? Why does the acidic character change? Pattern-learning handles 80% of p-Block questions.

Week 3: d-Block trends (IE, atomic radius, oxidation states, colour, magnetic properties) and then Metallurgy (principle-based — understand why each step happens).

For p-Block, make a single A4 sheet with Group 15/16/17/18 in columns. Fill in: allotropes, hydrides (structure + property), oxides (acidic/basic/amphoteric), oxoacids (structures). This one sheet replaces 40 pages of notes and is the highest-ROI revision activity for Inorganic.

For PYQs, specifically solve the last 5 years of JEE Main Inorganic questions sorted by subtopic — not by year. Doing all Coordination Compound questions together exposes the patterns faster than paper-by-paper revision.

Target score allocation: If you get 7 Inorganic questions in JEE Main, aim for 6 correct. Inorganic is more forgiving than Physical Chemistry because you can eliminate wrong options even with partial recall — use that.

Common Traps

Trap 1 — CO₃²⁻ vs CO₂ in Coordination Chemistry. When CO₂ is a ligand, it binds differently than carbonate. Students often confuse ambidentate ligands (SCN⁻ can bind via S or N; NO₂⁻ via N or O) with bidentate ligands. Linkage isomerism is only possible with ambidentate ligands, not bidentate ones.

Trap 2 — Colour and d-d transitions. Students write “all d¹⁰ complexes are colourless” — this is only true for d-d transitions. However, some d¹⁰ complexes show colour due to charge transfer transitions (e.g., CdS is yellow). JEE Advanced has tested this distinction.

Trap 3 — Ionic vs Covalent character in s-Block. LiCl is more covalent than NaCl — students get confused because Li⁺ is a small cation with high charge density, so it polarises the Cl⁻ anion more. Fajan’s rules: small cation, large anion, high charge → more covalent. Don’t flip this.

Trap 4 — Oxidation state in complex ions. In $[\text{Fe}(\text{CO})_5]$ , CO is a neutral ligand, charge of the complex is 0, so Fe is in the 0 oxidation state. Students reflexively assign Fe²⁺ or Fe³⁺. Always check: neutral complex + only neutral ligands = metal in 0 oxidation state.

Trap 5 — Counting dπ–pπ bonds in p-Block. In SO₃, the structure has S=O double bonds — students often forget that S uses empty d-orbitals for back-bonding. The question “which molecule has the highest bond order for S–O?” requires comparing SO₂, SO₃, SO₄²⁻, SO₃²⁻ by counting resonance structures, not by guessing.

The biggest overall trap in Inorganic is overconfidence. Students read a property, feel like they know it, and then get caught by a slight variation in the question. The remedy is straightforward: after reading any property, immediately ask “under what conditions does this break down?” The exceptions in Inorganic are where the marks are.