Physical Chemistry:   ~35%    Numerical heavy, concept dependent
Organic Chemistry:    ~35%    Mechanism-based, logical
Inorganic Chemistry:  ~30%    Memory + understanding periodic trends

Mole = 6.022×10²³ particles (Avogadro's number)
Molar mass: mass of 1 mole in grams = numerical value of molecular weight

Concentration units:
  Molarity (M): moles of solute per litre of solution
  Molality (m): moles of solute per kg of solvent
  Mole fraction: moles of component / total moles
  Normality (N): gram equivalents per litre

Limiting reagent: Consumed first, determines product amount
% yield = (actual yield / theoretical yield) × 100

First law: ΔU = q + w  (internal energy change = heat + work)
  w = -PΔV for expansion work
  At constant pressure: q_p = ΔH (enthalpy change)
  At constant volume: q_v = ΔU

Hess's Law: ΔH is path-independent
  ΔH_reaction = ΣΔH_f(products) - ΣΔH_f(reactants)

Spontaneity (Second law):
  ΔG = ΔH - TΔS
  ΔG < 0: Spontaneous, ΔG > 0: Non-spontaneous, ΔG = 0: Equilibrium
  
Bond energy: Energy to break 1 mole of bonds in gaseous state
  ΔH_reaction = ΣBE(bonds broken) - ΣBE(bonds formed)

Equilibrium constant (Kc): [Products]^coeff / [Reactants]^coeff
  Only concentration terms (no pure solids/liquids)
  
Kp = Kc(RT)^Δn    (Δn = moles gas products - moles gas reactants)

Le Chatelier's Principle:
  Increase concentration of reactant → shifts right (more product)
  Increase temperature for endothermic reaction → shifts right
  Increase pressure → shifts to side with fewer moles of gas

Ka (acid dissociation): Stronger acid = higher Ka = lower pKa
Kb (base dissociation): Stronger base = higher Kb
pH = -log[H⁺],  pOH = -log[OH⁻],  pH + pOH = 14 at 25°C
Henderson-Hasselbalch: pH = pKa + log([A⁻]/[HA])  (buffer equation)

Standard electrode potential (E°):
  Positive E°: Better oxidising agent (gains electrons easily)
  Negative E°: Better reducing agent (loses electrons easily)
  
EMF = E°_cathode - E°_anode  (reduction potentials)

Nernst equation: E = E° - (0.0592/n)log Q  (at 25°C)
ΔG° = -nFE°   (F = 96500 C/mol)

Faraday's laws of electrolysis:
  Mass deposited = (M/nF) × I × t
  M = molar mass, n = electrons, I = current, t = time

SN2 (Bimolecular Nucleophilic Substitution):
  One step, backside attack, inversion of configuration (Walden inversion)
  Favoured by: Primary substrate, strong nucleophile, polar aprotic solvent
  Rate = k[substrate][nucleophile]

SN1 (Unimolecular Nucleophilic Substitution):
  Two steps, carbocation intermediate, racemisation
  Favoured by: Tertiary substrate, weak nucleophile, polar protic solvent
  Rate = k[substrate] only
  Carbocation stability: 3° > 2° > 1° > methyl

E2 (Bimolecular Elimination):
  Concerted, anti-periplanar geometry required
  Strong base, primary substrate, high temperature
  Zaitsev rule: More substituted alkene preferred (unless bulky base)

E1 (Unimolecular Elimination):
  Two steps, carbocation intermediate
  Tertiary substrate, weak base, polar protic solvent
  Also follows Zaitsev rule

Aldol condensation: Aldehyde/ketone + base → β-hydroxy carbonyl
Cannizzaro: Non-enolizable aldehyde + strong base → acid + alcohol (disproportionation)
Clemmensen reduction: Carbonyl → CH₂ (Zn-Hg/HCl)
Wolff-Kishner: Carbonyl → CH₂ (N₂H₄/KOH)
Grignard reaction: RMgX + carbonyl → alcohol
Diels-Alder: Diene + dienophile → cyclohexene (cycloaddition)
Friedel-Crafts alkylation: Benzene + RX/AlCl₃ → alkylbenzene
Friedel-Crafts acylation: Benzene + RCOCl/AlCl₃ → aryl ketone
Reimer-Tiemann: Phenol + CHCl₃/NaOH → salicylaldehyde
Hoffmann bromamide: RCONH₂ + Br₂/NaOH → RNH₂ (amine, one carbon less)

Benzene resonance: 6 equivalent C-C bonds (1.5 bond order)
Aromaticity (Hückel): Planar, cyclic, fully conjugated, 4n+2 π electrons
  n=0: 2 electrons (cyclopropenyl cation)
  n=1: 6 electrons (benzene ✓)
  n=2: 10 electrons (naphthalene ✓)

EAS (Electrophilic Aromatic Substitution):
  Activating groups (ortho/para directors): -OH, -OR, -NH₂, -CH₃, -X (halogens activate weak, direct o/p)
  Deactivating groups (meta directors): -NO₂, -CHO, -COOH, -CN, -SO₃H
  
  Mechanism: Benzene attacks electrophile → arenium ion → deprotonation → product

Atomic radius: Increases down group, decreases across period (left to right)
Ionisation energy: Decreases down group, increases left to right
Exception: IE of O < N (N has stable half-filled 2p³)
           IE of Mg < Al (Mg 3s², Al 3p¹)

Electronegativity: Increases up and right (F is highest: 4.0)
Electron affinity: Generally increases up and right
  Exceptions: Noble gases, N (stable half-filled), F < Cl (small size, electron repulsion)

VSEPR: Shape from electron pairs (bonding + lone pairs)
  2 pairs: Linear (BeCl₂)
  3 pairs: Trigonal planar (BF₃) or bent with 1 LP (SO₂)
  4 pairs: Tetrahedral (CH₄), pyramidal (NH₃), bent (H₂O)
  5 pairs: Trigonal bipyramidal or see-saw, T-shaped, linear
  6 pairs: Octahedral or square pyramidal or square planar

Crystal Field Theory:
  Octahedral: d orbitals split into t₂g (lower, 3 orbitals) + eg (higher, 2 orbitals)
  Strong field ligands (large Δ): CN⁻, CO, NO⁺ — low spin
  Weak field ligands (small Δ): F⁻, Cl⁻, Br⁻, I⁻ — high spin
  Spectrochemical series: I⁻ < Br⁻ < Cl⁻ < F⁻ < OH⁻ < ox < H₂O < py < NH₃ < en < CN⁻ < CO

Physical Chemistry: Master concepts first, then practice numericals
  Books: NCERT, P Atkins (reference), Narendra Awasthi numericals
  
Organic Chemistry: Draw mechanisms, don't memorise products
  Books: NCERT, MS Chauhan (reactions), Clayden (reference for Advanced)
  
Inorganic Chemistry: NCERT is primary source — read thoroughly
  Focus: p-block, d-block, coordination compounds
  Books: NCERT + J D Lee for Advanced

Practice approach:
  Solve previous year papers (2010-2024) — many concepts repeat
  JEE Main: 1 hour per 30 questions target (2 min each)
  JEE Advanced: Focus on multi-concept problems