Chemical Bonding for NEET: Class 11 Chapter 4 Guide
Chemical bonding is Unit 3 of the official NEET (UG) Chemistry syllabus, and it is taught in one NCERT chapter: Class 11 Chemistry, Unit 4, Chemical Bonding and Molecular Structure. NCERT defines a chemical bond as the attractive force that holds atoms or ions together in a chemical species. This guide matches each syllabus phrase to its NCERT section, gives you the shape, hybridisation and bond order tables in one place, flags the two syllabus lines the chapter barely covers, and ends with a revision plan you can start this week.
What is chemical bonding in the NEET syllabus?
Chemical bonding is Unit 3, Chemical Bonding and Molecular Structure, of the Chemistry part of the NEET (UG) syllabus linked from the official NEET site. That file is headed "Syllabus for NEET (UG) 2025", and the NEET (UG) 2026 Information Bulletin says in its FAQ that there is no change in the syllabus for 2026 with respect to the previous year. As of 21 October 2026, the NEET (UG) public notices carry nothing about the 2027 cycle, so this is the wording to study from until NTA publishes a new one.
The syllabus unit has six parts. Here is where each one lives in the NCERT chemical bonding chapter (Class 11 Chemistry Part I, Unit 4, Reprint 2026-27).
| Syllabus phrase | NCERT Unit 4 section | What it covers |
|---|---|---|
| Kossel-Lewis approach, ionic and covalent bonds | 4.1 Kossel-Lewis Approach | Octet rule, Lewis structures, formal charge, limits of the octet rule |
| Ionic bonding, factors, lattice enthalpy | 4.2 Ionic or Electrovalent Bond | Ionisation and electron gain enthalpy, lattice enthalpy |
| Electronegativity, Fajan's rule, dipole moment | 4.3 Bond Parameters (4.3.6 Polarity of Bonds) | Bond length, angle, enthalpy, order, resonance, dipole moment, Fajans rules |
| VSEPR theory and shapes of simple molecules | 4.4 VSEPR Theory | Tables 4.6, 4.7 and 4.8 of shapes |
| Valence bond theory, hybridisation with s, p and d orbitals, resonance | 4.5 Valence Bond Theory, 4.6 Hybridisation | Orbital overlap, sigma and pi bonds, sp to sp3d2 |
| Molecular orbital theory, bond order, bond length, bond energy | 4.7 Molecular Orbital Theory, 4.8 Homonuclear Diatomic Molecules | LCAO, bonding and antibonding orbitals, H2 to Ne2 |
| Hydrogen bonding and its applications | 4.9 Hydrogen Bonding | Cause, intermolecular and intramolecular types |
| Elementary idea of metallic bonding | No section in Unit 4 | See the next section |
The chapter is long: 36 pages in the PDF, with 22 numbered figures. It is also why the Class 11 backlog guide puts chemical bonding in its re-learn bucket, the chapters worth a full, slow pass rather than a quick patch.
Two syllabus lines the chapter does not fully cover
The first one is plain. The syllabus ends Unit 3 with "elementary idea of metallic bonding". NCERT Unit 4 runs from 4.1 to 4.9 and has no section on metallic bonding at all; the word "metal" only appears there when the book talks about metal ions in ionic compounds. So the chapter alone will not cover that line. Keep it to the elementary level the syllabus asks for, and ask your teacher to point you to an NCERT-based reading for it.
The second one is about wording. The syllabus says "calculation of lattice enthalpy". NCERT defines lattice enthalpy as the energy needed to completely separate one mole of a solid ionic compound into gaseous ions, gives the value for NaCl as 788 kJ per mol, and then says it is not possible to calculate lattice enthalpy directly from the forces of attraction and repulsion alone, because crystal geometry has to be included. Read section 4.2 carefully: a question on lattice enthalpy will expect the definition, the NaCl figure and the idea that a high lattice enthalpy stabilises an ionic solid.
Neither line is a reason to panic. Both are reasons to read the syllabus next to the book, not just the book. Our NEET 2027 deleted syllabus guide shows the same method for the topics that really were removed.
How much is chemical bonding worth in NEET?
Nobody official publishes chapter-wise weightage. The NEET (UG) 2026 Information Bulletin fixes the paper by subject only: Physics 45 questions, Chemistry 45, Biology 90, for 180 questions in 180 minutes and 720 marks. Any per-chapter number you see online comes from someone counting old papers, not from NTA.
Two things are certain, though. Chemistry carries 180 marks, and the bulletin's tie-break rule ranks candidates with equal scores by Biology first, then Chemistry, then Physics. And chemical bonding reaches beyond its own unit: NCERT's hybridisation table already uses coordination complexes such as [Ni(CN)4]2- and [Co(NH3)6]3+, and the book says VSEPR predicts the geometry of p-block compounds especially accurately, so a gap here shows up in other units too. Our NEET Chemistry questions guide lays out how the 45 questions and the three blocks of the syllabus fit together.
A wrong answer costs one mark, and a half-remembered shape or magnetic property is exactly where students are tempted to guess. The negative marking guide shows when a guess is worth it.
What are the main types of chemical bonds?
The main types of chemical bonds in this chapter are ionic bonds, covalent bonds and hydrogen bonds. An ionic bond forms when electrons are transferred and the oppositely charged ions attract. A covalent bond forms when two atoms share a pair of electrons. A hydrogen bond is a weaker attraction between a hydrogen atom bonded to F, O or N and another such atom.
In chemical bonding, most real bonds sit between the extremes, and NCERT says so directly: no bond is completely covalent or completely ionic. When the two atoms differ in electronegativity, the shared pair shifts towards one of them, the bond becomes polar and the molecule can have a dipole moment.
Ionic bonds can have partial covalent character too. NCERT gives Fajans rules for when that happens:
- The smaller the cation and the larger the anion, the greater the covalent character.
- The greater the charge on the cation, the greater the covalent character.
- For cations of the same size and charge, one with the (n-1)d^n ns^0 configuration of transition metals is more polarising than one with the noble gas configuration of alkali and alkaline earth metals.
The octet rule explains a lot but not everything. NCERT lists three kinds of exception: the incomplete octet (LiCl, BeH2, BCl3), odd-electron molecules (NO and NO2) and the expanded octet (PF5, SF6, H2SO4). It also notes that the octet rule says nothing about shape, which is where VSEPR comes in.
The bond numbers NCERT prints
Bond parameters are where chemical bonding turns into numbers, and NEET likes comparing them. These are NCERT's own values from section 4.3.
| Bond or molecule | Value in NCERT | Table or section |
|---|---|---|
| C-C single bond | 154 pm | Table 4.2 |
| C=C double bond | 133 pm | Table 4.2 |
| C≡C triple bond | 120 pm | Table 4.2 |
| H2 bond length | 74 pm | Table 4.3 |
| N2 bond length | 109 pm | Table 4.3 |
| H-H bond enthalpy | 435.8 kJ per mol | 4.3.3 |
| O=O bond enthalpy | 498 kJ per mol | 4.3.3 |
| N≡N bond enthalpy | 946.0 kJ per mol | 4.3.3 |
| H-Cl bond enthalpy | 431.0 kJ per mol | 4.3.3 |
The rule that ties them together is in section 4.3.4: as bond order increases, bond enthalpy increases and bond length decreases. The carbon rows show it cleanly, 154 to 133 to 120 pm. NCERT also gives a shortcut: isoelectronic molecules and ions have the same bond order, so F2 and O2(2-) both have bond order 1, and N2, CO and NO+ all have bond order 3.
One small thing to know before an exam. NCERT gives slightly different values for the same bond in different places: H2 is 435.8 kJ per mol in section 4.3.3 but 438 in section 4.8, and N2 is 946.0 in section 4.3.3 but 945 in Figure 4.21. If a question gives you a value, use that one.
How do you predict a shape with VSEPR theory?
VSEPR (valence shell electron pair repulsion) theory is the first tool chemical bonding gives you for shapes. It predicts a molecule's shape from the number of electron pairs around the central atom. Electron pairs repel each other and move as far apart as possible, and lone pairs repel more strongly than bonding pairs. Use these steps for any simple molecule.
- Find the central atom and count its valence-shell electron pairs. Count bonding pairs and lone pairs together.
- Treat a double or triple bond as one pair. NCERT calls it a single super pair.
- Read the arrangement from the total. Two pairs is linear, three is trigonal planar, four is tetrahedral, five is trigonal bipyramidal, six is octahedral (Table 4.6).
- Name the shape from the atoms only. If there are lone pairs, the shape is what the atoms make, not the arrangement of pairs (Table 4.7).
- Adjust the angle. Repulsion falls in the order lone pair-lone pair, then lone pair-bond pair, then bond pair-bond pair, so lone pairs squeeze bond angles below the ideal value.
Here are the shapes NCERT tabulates, with its own examples.
| Type | Bond pairs | Lone pairs | Shape | NCERT example |
|---|---|---|---|---|
| AB2 | 2 | 0 | Linear | BeCl2, HgCl2 |
| AB3 | 3 | 0 | Trigonal planar | BF3 |
| AB4 | 4 | 0 | Tetrahedral | CH4, NH4+ |
| AB5 | 5 | 0 | Trigonal bipyramidal | PCl5 |
| AB6 | 6 | 0 | Octahedral | SF6 |
| AB2E | 2 | 1 | Bent | SO2, O3 |
| AB3E | 3 | 1 | Trigonal pyramidal | NH3 |
| AB2E2 | 2 | 2 | Bent | H2O |
| AB4E | 4 | 1 | See-saw | SF4 |
| AB3E2 | 3 | 2 | T-shape | ClF3 |
| AB5E | 5 | 1 | Square pyramid | BrF5 |
| AB4E2 | 4 | 2 | Square planar | XeF4 |
Table 4.8 gives the angles to remember: SO2 drops to 119.5 degrees from 120, NH3 to 107 from 109.5, and H2O to 104.5 from 109.5. In SF4, the lone pair sits in an equatorial position because that gives fewer lone pair-bond pair repulsions at 90 degrees.
Hybridisation: which type gives which shape?
Hybridisation is the mixing of atomic orbitals of slightly different energies on one atom to form new orbitals of equal energy, and it is how valence bond theory, the second big idea in chemical bonding, explains the shapes VSEPR predicts. NCERT's sections 4.6.1 to 4.6.3 give one example for each type.
| Hybridisation | Orbitals mixed | Shape | NCERT example |
|---|---|---|---|
| sp | s + p | Linear, 180 degrees | BeCl2 |
| sp2 | s + 2 p | Trigonal planar, 120 degrees | BCl3 |
| sp3 | s + 3 p | Tetrahedral, 109.5 degrees | CH4 (also NH3 and H2O, with lone pairs) |
| dsp2 | d + s + 2 p | Square planar | [Ni(CN)4]2-, [PtCl4]2- |
| sp3d | s + 3 p + d | Trigonal bipyramidal | PF5, PCl5 |
| sp3d2 | s + 3 p + 2 d | Square pyramidal or octahedral | BrF5; SF6 |
Two details NCERT spells out are worth a mark each. In each sp3 orbital there is 25% s character and 75% p character. And in ethene the carbon-carbon bond is one sp2-sp2 sigma bond plus one pi bond, with a bond length of 134 pm, while ethane's C-C single bond is 154 pm.
How do you find bond order with molecular orbital theory?
In molecular orbital theory, atomic orbitals combine into orbitals that belong to the whole molecule: bonding orbitals, which are lower in energy, and antibonding orbitals, which are higher. Bond order is half of the number of electrons in bonding orbitals minus the number in antibonding orbitals. A positive bond order means a stable molecule; zero or negative means it is unstable.
That one formula answers most NEET questions on chemical bonding in diatomic molecules. He2 has two bonding and two antibonding electrons, so its bond order is zero and it does not exist. Li2 works out to 1, C2 to 2, O2 to 2.
The order in which orbitals fill changes across the period. For O2 and F2, the sigma 2pz orbital is lower than the two pi 2p orbitals. For Li2, Be2, B2, C2 and N2, it is the other way round: sigma 2pz sits higher than pi 2px and pi 2py. That switch is why NCERT notes that the double bond in C2 is made of two pi bonds, with no sigma bond, unlike most double bonds.
Read the chart left to right and the rule from section 4.3.4 shows up in real numbers. N2, with the highest bond order, has the strongest bond and the shortest length (110 pm). F2, with bond order 1, has the weakest bond of the five. Figure 4.21 also gives Ne2 a bond order of 0.
Magnetism is the other question MO theory answers. If every molecular orbital is doubly occupied, the molecule is diamagnetic. If one or more is singly occupied, it is paramagnetic. O2 has 16 electrons, ten in bonding and six in antibonding orbitals, giving bond order 2, and its two unpaired electrons in the pi star orbitals make it paramagnetic. NCERT calls that a prediction that matches experiment.
Dipole moment: why NH3 beats NF3
Dipole moment is where chemical bonding meets molecular shape. It is the product of the charge and the distance between the centres of positive and negative charge, and it is usually given in debye units. For a molecule with more than one bond, it is the vector sum of the bond dipoles, so shape decides the answer. These are NCERT's Table 4.5 values, with the experimental values from the US National Institute of Standards and Technology's list of experimental dipole moments beside them.
| Molecule | Shape | NCERT, Table 4.5 (D) | NIST CCCBDB (D) |
|---|---|---|---|
| H2O | Bent | 1.85 | 1.857 |
| NH3 | Trigonal pyramidal | 1.47 | 1.476 |
| NF3 | Trigonal pyramidal | 0.23 | 0.235 |
| HF | Linear | 1.78 | 1.827 |
| CO2 | Linear | 0 | 0.000 |
| BF3 | Trigonal planar | 0 | 0.000 |
| CH4 | Tetrahedral | 0 | 0.000 |
The NH3 and NF3 pair is the classic trap. Fluorine is more electronegative than nitrogen, so you might expect NF3 to be more polar. It is not. In NH3 the lone pair's orbital dipole points the same way as the resultant of the three N-H bond dipoles, so they add up. In NF3 it points the opposite way and cancels much of the N-F bond moments. CO2 and BF3 have polar bonds but zero dipole moment, because their bond dipoles cancel by symmetry. For HF, NIST lists 1.827 D against NCERT's 1.78; in the exam, use the NCERT value.
Hydrogen bonding in two types
Hydrogen bonding is the last section of chemical bonding in NCERT. A hydrogen bond is the attractive force that binds a hydrogen atom of one molecule to an electronegative atom (F, O or N) of another molecule. It is weaker than a covalent bond. NCERT notes that its strength is greatest in the solid state and least in the gaseous state.
There are two types. Intermolecular hydrogen bonds form between two molecules of the same or different compounds, as in HF, alcohol or water. Intramolecular hydrogen bonds form within one molecule, between two highly electronegative atoms that hydrogen sits between. NCERT's example is o-nitrophenol, where the hydrogen sits between two oxygen atoms. Learn that one example by name; it is the one questions use.
Eight mistakes that cost marks in chemical bonding
- Calling NH3 tetrahedral. The electron pairs are tetrahedral; the shape is trigonal pyramidal, at 107 degrees.
- Giving NF3 the larger dipole moment. NH3 is 1.47 D, NF3 is 0.23 D.
- Calling O2 diamagnetic. MO theory and experiment both say paramagnetic. B2 is paramagnetic too.
- Assuming every double bond has a sigma bond. In C2, NCERT says both bonds are pi bonds.
- Calling BF3 or CO2 polar molecules. Their bonds are polar, but the dipole moment is zero.
- Mixing up SF4, ClF3 and XeF4. See-saw, T-shape and square planar, in that order.
- Forgetting the isoelectronic shortcut. N2, CO and NO+ all have bond order 3; F2 and O2(2-) have bond order 1.
- Saying He2 is just unstable. Its bond order is zero, and NCERT says it does not exist.
How should you revise chemical bonding?
Plan on three or four sessions of chemical bonding, not one. This chapter rewards drawing more than reading.
- Read NCERT Unit 4 once, sections 4.1 to 4.9. Mark every table and every named molecule.
- Rebuild Tables 4.6 and 4.7 from memory. Write type, pairs, shape and example for all twelve rows, then check. A set of [NEET flashcards](/blogs/neet-flashcards/) with the formula on one side and the shape on the other works well here.
- Draw ten molecules. BeCl2, BF3, CH4, NH3, H2O, PCl5, SF4, ClF3, XeF4 and SF6, each with lone pairs, shape, angle and hybridisation.
- Write the MO configuration of B2 to F2 and calculate each bond order. Then mark which are paramagnetic and compare with Figure 4.21.
- Answer the NCERT exercise questions in writing. The ones on He2, the bond order of N2, O2, O2+ and O2-, PCl5's axial bonds and hydrogen bonding are the most NEET-like.
- Solve timed MCQs on the chapter. Start with previous NEET papers; the [previous year question papers guide](/blogs/neet-2027-previous-year-question-papers/) shows where to find the official ones.
If you are new to reading NCERT this closely, the guide to studying NCERT for NEET 2027 shows the method, and futureMBBS explains what the NCERT book is and why NEET leans on it. For where this unit sits in your year, the NEET 2027 Chemistry preparation strategy lays out the order of the units, futureMBBS's NEET syllabus guide puts all three subjects in one view, and its how to prepare for NEET guide covers the wider plan.
Know the shapes, or only recognise them? Timed questions tell you which. NEETsheet is our NEET UG prep app, with NCERT-aligned questions and full-length mocks that show which chapters keep costing you marks.
Sources
Every syllabus line, name and number above comes from these official documents, opened and read on 21 October 2026.
- National Testing Agency, NEET (UG) syllabus file linked from neet.nta.nic.in, headed "Syllabus for NEET (UG) 2025" (Chemistry Unit 3, Chemical Bonding and Molecular Structure): https://cdnbbsr.s3waas.gov.in/s37bc1ec1d9c3426357e69acd5bf320061/uploads/2026/01/20260102588210790.pdf
- National Testing Agency, Information Bulletin NEET (UG) 2026 (pattern: Chemistry 45 questions and 180 of 720 marks; plus four and minus one marking; tie-break order; syllabus FAQ stating no change for 2026): https://cdnbbsr.s3waas.gov.in/s37bc1ec1d9c3426357e69acd5bf320061/uploads/2026/02/202602231394640855.pdf
- National Testing Agency, NEET (UG) public notices, checked on 21 October 2026 for any NEET (UG) 2027 notice: https://neet.nta.nic.in/public-notices/
- NCERT, Chemistry Part I, Class 11, Unit 4 "Chemical Bonding and Molecular Structure" (Reprint 2026-27): https://ncert.nic.in/textbook/pdf/kech104.pdf
- National Institute of Standards and Technology, Computational Chemistry Comparison and Benchmark Database, list of experimental dipole moments (Release 22): https://cccbdb.nist.gov/diplistx.asp
Frequently Asked Questions
NCERT Class 11 Chemistry Part I, Unit 4, titled Chemical Bonding and Molecular Structure. Its nine sections cover the Kossel-Lewis approach, ionic bonds, bond parameters, VSEPR theory, valence bond theory, hybridisation, molecular orbital theory, homonuclear diatomic molecules and hydrogen bonding. In the NEET (UG) Chemistry syllabus the same topic is Unit 3.
The main types are ionic bonds, formed by transfer of electrons and attraction between ions; covalent bonds, formed by sharing a pair of electrons; and hydrogen bonds, a weaker attraction involving hydrogen bonded to F, O or N. NCERT stresses that real bonds are rarely purely ionic or purely covalent.
Bond order is half of the difference between the number of electrons in bonding molecular orbitals and the number in antibonding molecular orbitals. For O2 that is half of 10 minus 6, which is 2. A positive bond order means a stable molecule, and a higher bond order means a shorter, stronger bond.
In molecular orbital theory, the last two electrons of O2 go singly into the two pi star 2p orbitals, so the molecule has two unpaired electrons. Any molecule with singly occupied molecular orbitals is attracted by a magnetic field. NCERT notes that this prediction matches what is seen in experiments.
Yes. Unit 3 of the NEET (UG) Chemistry syllabus ends with an elementary idea of metallic bonding. NCERT Class 11 Chemistry Unit 4, however, has no section on metallic bonding, so the chapter alone does not cover that line. Keep it to the elementary level the syllabus asks for.
If you are revising Class 11 Chemistry this term, NEETsheet is our NEET UG prep app: NCERT-aligned questions chapter by chapter, timed mocks, and a clear view of where your marks go.
