ATOMIC RADIUS (pm):
  Li(152) Na(186) K(227) | Be(112) Mg(160) Ca(197) | B(87) Al(143)
  C(77) Si(118) | N(75) P(110) | O(73) S(103) | F(72) Cl(99)

IONISATION ENERGY (kJ/mol, first):
  Trend: increases → across period | decreases ↓ down group
  Exceptions: IE₁(B) < IE₁(Be) | IE₁(O) < IE₁(N) | IE₁(Tl) < IE₁(In)

ELECTRONEGATIVITY (Pauling scale):
  F(3.98) O(3.44) N(3.04) Cl(3.16) Br(2.96) C(2.55) H(2.2) Na(0.93)

IDENTIFICATION TESTS:
  Primary amine: carbylamine test (CHCl₃ + KOH + R-NH₂ → isocyanide, foul smell)
  Aldehyde: Tollens (silver mirror) | Fehling (red precipitate)
  Ketone: 2,4-DNP (orange/red precipitate)
  Unsaturation: decolourises Br₂/CCl₄
  Phenol: FeCl₃ (violet colour) | doesn't react with NaHCO₃
  Carboxylic acid: reacts with NaHCO₃ (CO₂ effervescence)

COLOUR GUIDE (inorganic — NEET loves these):
  CrO₄²⁻: yellow | Cr₂O₇²⁻: orange | Cr³⁺: green | CrO₃: dark red
  MnO₄⁻: purple | MnO₄²⁻: green | Mn²⁺: pink/light pink
  Fe²⁺: pale green | Fe³⁺: yellow-brown | Cu²⁺: blue | Ni²⁺: green

FLAME TEST COLOURS:
  Li: crimson red | Na: golden yellow | K: lilac/violet
  Ca: brick red | Sr: crimson red | Ba: apple green | Cu: blue-green

ENTHALPY:
  ΔH = ΔU + Δ(PV) = ΔU + ΔngRT (for ideal gases)
  Hess's law: ΔH_rxn = ΣΔH_products - ΣΔH_reactants

ENTROPY AND GIBBS ENERGY:
  ΔS > 0: disorder increases (solid→liquid→gas, dissolution, more moles of gas)
  ΔG = ΔH - TΔS
  ΔG < 0: spontaneous | ΔG > 0: non-spontaneous | ΔG = 0: equilibrium

THERMODYNAMIC PREDICTIONS:
  ΔH < 0, ΔS > 0: always spontaneous (ΔG always negative)
  ΔH > 0, ΔS < 0: never spontaneous
  ΔH < 0, ΔS < 0: spontaneous at low T (enthalpy driven)
  ΔH > 0, ΔS > 0: spontaneous at high T (entropy driven)

CELL REACTION AND EMF:
  E°cell = E°cathode - E°anode (standard reduction potentials)
  Positive E°cell → spontaneous reaction

NERNST EQUATION: E = E° - (0.0592/n) log Q (at 25°C)
  At equilibrium: E = 0, so E° = (0.0592/n) log Keq

FARADAY'S LAWS:
  Q = I × t (charge = current × time)
  Mass deposited: m = (M × I × t) / (n × 96500)
  
  1 Faraday = 96500 C = charge of 1 mole of electrons
  
CONDUCTANCE:
  Specific conductance: κ = 1/ρ (reciprocal of resistivity)
  Molar conductance: Λm = (κ × 1000) / M
  Strong electrolytes: Λm increases linearly with dilution
  Weak electrolytes: Λm increases sharply at high dilution (Kohlrausch law)