Class 11 NCERT Chemistry — 50 Re-NEET 2026 Chemistry Quick Revision Lines

---

Some Basic Concepts of Chemistry

This section of the Re-NEET 2026 Chemistry quick revision list covers the calculation-heavy lines that appear in Physical Chemistry MCQs.

1. One mole of any substance contains 6.022 × 10²³ particles — this is Avogadro’s number (Nₐ).
2. Molarity (M) = moles of solute / volume of solution in litres. It changes with temperature.
3. Molality (m) = moles of solute / mass of solvent in kg. It does NOT change with temperature.
4. Mole fraction of a component = moles of that component / total moles of all components. Sum of all mole fractions = 1.
5. Empirical formula gives the simplest whole-number ratio of atoms; molecular formula gives the actual number of atoms.
6. The limiting reagent is the reactant that is completely consumed first and determines the amount of product formed.
7. Percentage yield = (actual yield / theoretical yield) × 100.

---

Structure of Atom

Structure of Atom is compact but consistent — Re-NEET 2026 Chemistry quick revision must include Bohr’s model, uncertainty principle, and Aufbau principle.

8. Bohr’s model postulates: electrons revolve in fixed circular orbits; energy is absorbed or emitted only when electrons jump between orbits.
9. Heisenberg’s Uncertainty Principle: it is impossible to determine simultaneously the exact position and exact momentum of a moving electron. Δx · Δp ≥ h/4π.
10. An orbital is a three-dimensional region around the nucleus where the probability of finding an electron is maximum (≥90%).
11. Aufbau principle: electrons fill orbitals in order of increasing energy — 1s, 2s, 2p, 3s, 3p, 4s, 3d…
12. Hund’s rule: electrons occupy orbitals of equal energy singly before pairing, and all singly occupied orbitals have the same spin.
13. Pauli’s Exclusion Principle: no two electrons in an atom can have the same set of all four quantum numbers.
14. The s-block elements have their last electron in an s-orbital (Groups 1 and 2); p-block in p-orbital (Groups 13–18).

---

Chemical Bonding and Molecular Structure

Chemical Bonding is one of the highest-weightage chapters in any Re-NEET 2026 Chemistry quick revision session — expect 3–4 direct questions.

15. Ionic bond forms by complete transfer of electrons; covalent bond forms by sharing of electrons.
16. Electronegativity difference > 1.7 → predominantly ionic bond; < 1.7 → predominantly covalent bond.
17. VSEPR theory: the shape of a molecule depends on the number of bond pairs and lone pairs around the central atom. Lone pairs repel more than bond pairs.
18. Shape of NH₃ is trigonal pyramidal (3 bond pairs + 1 lone pair); H₂O is bent/V-shaped (2 bond pairs + 2 lone pairs).
19. Hybridisation of BF₃ is sp² (planar triangular); CH₄ is sp³ (tetrahedral); C₂H₂ (acetylene) is sp (linear).
20. Hydrogen bond is the electrostatic attraction between the H atom covalently bonded to a highly electronegative atom (N, O, F) and the electronegative atom of another molecule.
21. Resonance structures are two or more Lewis structures that collectively describe the electronic structure of a single molecule — e.g., O₃, SO₃, benzene.

---

States of Matter

22. Boyle’s Law: at constant temperature, pressure is inversely proportional to volume — PV = constant.
23. Charles’s Law: at constant pressure, volume is directly proportional to absolute temperature — V/T = constant.
24. Ideal Gas Equation: PV = nRT. R = 8.314 J mol⁻¹ K⁻¹ = 0.0821 L atm mol⁻¹ K⁻¹.
25. Van der Waals equation: (P + an²/V²)(V − nb) = nRT. ‘a’ corrects for intermolecular attractions; ‘b’ corrects for molecular volume.
26. Critical temperature (Tₓ): the temperature above which a gas cannot be liquefied regardless of applied pressure. CO₂ has a critical temperature of 304.2 K.

---

Thermodynamics

Thermodynamics lines are heavily theory-based — a strong area in any Re-NEET 2026 Chemistry quick revision because they reward reading over calculation.

27. First Law of Thermodynamics: energy can neither be created nor destroyed — ΔU = q + w (IUPAC convention).
28. Enthalpy (H) = U + PV. At constant pressure, ΔH = qₚ (heat absorbed at constant pressure).
29. Hess’s Law: the total enthalpy change for a reaction is independent of the route taken — it depends only on the initial and final states.
30. Standard enthalpy of formation (ΔfH°) of any element in its most stable form is zero.
31. Second Law of Thermodynamics: the entropy of an isolated system always increases for a spontaneous process.
32. Gibbs free energy: ΔG = ΔH − TΔS. A reaction is spontaneous when ΔG < 0.

---

Equilibrium

33. Law of Chemical Equilibrium: Kc = [products]^stoichiometric coefficients / [reactants]^stoichiometric coefficients.
34. Le Chatelier’s Principle: if a system at equilibrium is disturbed, it shifts to minimise the disturbance.
35. pH = −log[H⁺]. For a neutral solution at 25°C, pH = 7. Acidic: pH < 7; Basic: pH > 7.
36. Buffer solution: resists change in pH on addition of small amounts of acid or base. Example: CH₃COOH + CH₃COONa.
37. Kw (ionic product of water) = [H⁺][OH⁻] = 1 × 10⁻¹⁴ at 25°C.
38. Common ion effect: suppression of ionisation of a weak acid or weak base by adding a salt with a common ion.

---

Redox Reactions

Redox lines are among the most direct NEET Chemistry NCERT important lines in the paper — OIL RIG and oxidation number rules appear frequently.

39. Oxidation = loss of electrons = increase in oxidation number. Reduction = gain of electrons = decrease in oxidation number.
40. OIL RIG: Oxidation Is Loss, Reduction Is Gain (of electrons).
41. Oxidation number of oxygen is −2 in most compounds (except in peroxides where it is −1, and in OF₂ where it is +2).
42. Oxidation number of hydrogen is +1 with non-metals and −1 with metals (metal hydrides).

---

s-Block Elements

For Re-NEET 2026 Inorganic Organic Physical revision, s-Block is a quick win — 5 lines cover everything NTA typically tests from this chapter.

43. Lithium shows anomalous behaviour among alkali metals and resembles magnesium — this is called the diagonal relationship.
44. Sodium hydroxide (caustic soda, NaOH) is manufactured by the Chlor-alkali process (electrolysis of brine).
45. Calcium carbonate (limestone) decomposes on heating to give quicklime (CaO) and CO₂ — this is thermal decomposition.
46. Plaster of Paris = CaSO₄·½H₂O. It sets on mixing with water to form gypsum (CaSO₄·2H₂O).

---

p-Block Elements (Class 11 portion)

47. Boron is a metalloid and a non-conductor of electricity at room temperature; it forms only covalent compounds.
48. Carbon shows catenation — the unique property of forming long chains, branched chains, and rings by bonding with itself.
49. Allotropes of carbon: diamond (hard, poor conductor), graphite (soft, good conductor), fullerenes (C₆₀ — Buckminsterfullerene).
50. Dinitrogen (N₂) is relatively inert due to the triple bond (N≡N, bond enthalpy = 941.4 kJ mol⁻¹) — one of the strongest bonds known.

Class 12 NCERT Chemistry — 50 More Re-NEET 2026 Chemistry Quick Revision Lines

---

Solutions

Solutions is where NEET Chemistry NCERT important lines and numerical formulas overlap — know both the theory and the formula for each colligative property.

51. Henry’s Law: at constant temperature, the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the solution. KH increases with temperature.
52. Raoult’s Law: the partial vapour pressure of a volatile component = mole fraction × vapour pressure of pure component.
53. Colligative properties depend only on the number of solute particles, not their nature: relative lowering of vapour pressure, elevation of boiling point, depression of freezing point, osmotic pressure.
54. van’t Hoff factor (i): i > 1 for electrolytes (dissociation); i < 1 for solutes that associate in solution.
55. Osmotic pressure (π) = iCRT, where C is molarity, R is gas constant, T is temperature in Kelvin.

---

Electrochemistry

For Re-NEET 2026 Chemistry quick revision, Electrochemistry is the single most formula-dense Class 12 chapter. These lines and your formula sheet together cover everything NTA tests.

56. Kohlrausch’s Law: the limiting molar conductivity of an electrolyte equals the sum of the limiting molar conductivities of its individual ions.
57. Nernst Equation: E_cell = E°_cell − (RT/nF) ln Q = E°_cell − (0.0592/n) log Q at 25°C.
58. Standard Hydrogen Electrode (SHE): E° = 0.00 V by convention — the reference electrode for all standard reduction potentials.
59. Faraday’s First Law of Electrolysis: the mass of substance deposited at an electrode is directly proportional to the quantity of charge passed.
60. Faraday’s constant = 96,500 C mol⁻¹ — the charge on one mole of electrons.
61. Electrolytic cells convert electrical energy into chemical energy; galvanic (voltaic) cells convert chemical energy into electrical energy.

---

Chemical Kinetics

Chemical Kinetics is a chapter where Re-NEET 2026 Chemistry last minute revision pays off quickly — the first-order formula and Arrhenius equation are tested almost every year.

62. Rate of reaction = change in concentration of reactant or product per unit time.
63. Order of reaction is experimentally determined; molecularity is the number of reacting species in an elementary step — it is always a positive integer.
64. First-order reaction: rate = k[A]. Half-life t½ = 0.693/k — it is independent of initial concentration.
65. Arrhenius equation: k = Ae^(−Ea/RT). Activation energy (Eₐ) is the minimum energy required for a reaction to occur.
66. A catalyst increases the rate of reaction by providing an alternative pathway with lower activation energy. It is not consumed in the reaction.

---

Surface Chemistry

Surface Chemistry is one of the most Re-NEET 2026 Chemistry quick revision-friendly chapters — short, fact-heavy, and frequently tested.

67. Adsorption: accumulation of molecules on the surface of a solid. Absorption involves uniform distribution throughout the bulk.
68. Physisorption is weak (van der Waals forces), reversible, multi-layer, and decreases with temperature.
69. Chemisorption involves formation of chemical bonds, is irreversible, mono-layer, and increases then decreases with temperature.
70. Freundlich adsorption isotherm: x/m = k·P^(1/n), where 1/n is between 0 and 1.
71. Colloids: particles with diameter 1–100 nm. Sols (solid in liquid), emulsions (liquid in liquid), gels (liquid in solid).
72. Tyndall effect: scattering of light by colloidal particles — used to distinguish colloids from true solutions.
73. Coagulation of colloids occurs by adding electrolytes, boiling, or by electrophoresis.

---

p-Block Elements (Class 12)

The NEET Chemistry NCERT important lines from p-Block are almost entirely factual — no numericals, pure recall. Very high return on revision time.

74. Interhalogen compounds are formed between two different halogens — e.g., ClF, BrF₃, IF₅. They are more reactive than halogens.
75. Ozone (O₃) is a powerful oxidising agent; it decomposes slowly to give O₂, and is used in purification of water and air.
76. Sulphuric acid (H₂SO₄) is manufactured by the Contact Process (SO₂ → SO₃ using V₂O₅ catalyst → H₂SO₄).
77. Nitric acid (HNO₃) is manufactured by the Ostwald Process (catalytic oxidation of NH₃ over Pt catalyst).
78. Phosphorus shows allotropy — white phosphorus (P₄, poisonous, glows in dark), red phosphorus (stable, non-poisonous).

---

d and f-Block Elements

For Re-NEET 2026 Chemistry quick revision, d and f-block lines are high-frequency — KMnO₄ and K₂Cr₂O₇ reactions appear nearly every year.

79. Transition elements (d-block) are elements whose atoms or ions have incompletely filled d-orbitals — they exhibit variable oxidation states.
80. Highest oxidation state of a transition metal corresponds to its group number — e.g., Mn shows +7 in KMnO₄.
81. KMnO₄ is a strong oxidising agent. It acts as a self-indicator in acidic medium (purple → colourless when reduced to Mn²⁺).
82. K₂Cr₂O₇ is a strong oxidising agent in acidic medium. The orange colour is due to Cr₂O₇²⁻ → green Cr³⁺ upon reduction.
83. Lanthanoid contraction: steady decrease in atomic and ionic radii across the lanthanoid series — due to poor shielding by 4f electrons.

---

Coordination Compounds

Coordination Compounds is a high-yield section for Re-NEET 2026 Chemistry last minute revision — compact chapter, predictable questions, 2–3 marks every year.

84. In a coordination compound, the central metal atom/ion is surrounded by ligands (Lewis bases that donate electron pairs).
85. Coordination number = number of ligand atoms directly bonded to the central metal atom.
86. Ambidentate ligands have two possible donor atoms — e.g., SCN⁻ (can bond through S or N), NO₂⁻ (through N or O).
87. Chelate complexes are formed by ligands that form rings with the central metal — e.g., EDTA is a hexadentate ligand.
88. Crystal Field Theory (CFT): d-orbitals split in the presence of ligands. Strong field ligands cause large splitting (Δ) → low-spin complex; weak field ligands cause small splitting → high-spin complex.
89. Werner’s theory: complexes have primary valency (oxidation state) and secondary valency (coordination number).

---

Organic Chemistry (Class 12)

Organic Chemistry is where NCERT Chemistry lines for NEET 2026 appear most directly as MCQ options — the exact reaction name or product is lifted from NCERT.

90. Haloalkanes: nucleophilic substitution (SN1 and SN2) and elimination (E1 and E2) are the primary reactions.
91. SN2 reaction: bimolecular, one step, inversion of configuration (Walden inversion), favoured by primary alkyl halides.
92. SN1 reaction: unimolecular, two steps, proceeds via carbocation intermediate, favoured by tertiary alkyl halides.
93. Alcohols show hydrogen bonding — they have higher boiling points than corresponding alkanes and ethers.
94. Lucas test: used to distinguish primary, secondary, and tertiary alcohols. Tertiary alcohol reacts immediately with ZnCl₂/HCl (turbidity); primary does not react at room temperature.
95. Aldol condensation: two molecules of an aldehyde or ketone (with α-hydrogen) condense in the presence of dilute NaOH to form a β-hydroxy carbonyl compound.
96. Cannizzaro reaction: aldehydes without α-hydrogen undergo disproportionation in concentrated NaOH — one molecule is oxidised to acid, another is reduced to alcohol.
97. Amines: primary amines react with nitrous acid to form diazonium salts (aromatic) or unstable diazonium compounds (aliphatic). Gabriel synthesis is used to prepare pure primary amines.
98. Carbylamine test: primary amines react with chloroform and KOH to form foul-smelling isocyanides (carbylamines) — test is specific to primary amines.
99. Biodegradable polymers: PHBV (polyhydroxybutyrate-co-hydroxyvalerate) and Nylon-2-nylon-6. Non-biodegradable: Nylon-6,6, Teflon, PVC, Bakelite.
100. Vitamins: Vitamin A, D, E, K are fat-soluble. Vitamin B-complex and C are water-soluble. Vitamin C (ascorbic acid) deficiency → scurvy; Vitamin D deficiency → rickets.