Independent topic page

p-Block Elements (Groups 13–18)

Use group oxidation-state logic and a small reaction bank to control the apparent factual load.

Portion InorganicFocus High-density statement, structure, and reaction-map marksTarget 45–75sPortion share 23.7%Trend Stable

Groups 13–18 trends and first-member anomalies; borax/diborane, silicones, ammonia/nitric acid, ozone/sulfuric acid, chlorine/HCl, and xenon compounds. Read every p-block statement set as trends × bonding × conditions — three filters, one answer.

How Advanced asks this

Compare oxidation states and inert-pair stability.
Determine shapes/bonding of diborane, oxoacids, interhalogens, and xenon fluorides.
Complete preparation, hydrolysis, disproportionation, and redox equations.
Order hydride stability/basicity/boiling point or oxide acidity.
Match industrial conditions and key compounds to observations.

Traps that leak marks

Extending first-member behaviour down a group.
Using d-orbital expansion as the only modern bonding explanation.
Ignoring conditions in halogen disproportionation.
Calling boric acid tribasic because it has three OH groups.
Confusing molecular shape with electron-pair geometry.
Calling boric acid tribasic from three OH groups
Ignoring medium in halogen disproportionation
Confusing molecular shape with electron-pair geometry

01. The ns²np¹–⁶ configurations set normal valencies; multiple bonding and small size make B, C, N, O, and F anomalous.

02. Down heavier groups, inert-pair effect stabilises oxidation states two units below the group maximum.

03. Structures, hydrolysis, acid-base behaviour, and redox character are more reliable than isolated colour or preparation facts.

04. Advanced frequently combines one familiar compound with an unfamiliar equation; electron count and oxidation state still solve it.

05. First-member anomalies and inert-pair effects are the real syllabus spine; extending B/C/N/O/F behaviour blindly down the group is the classic fail.

06. Structures (diborane, oxoacids, interhalogens, xenon fluorides) score when electron count and VSEPR join periodicity — bonding is not optional decoration.

07. Disproportionation, hydrolysis and industrial conditions are reaction chemistry under constraints; reagents without conditions are incomplete answers.

Official · 2026

Syllabus for this topic

Official syllabus points for p-Block Elements (Groups 13–18) only — not the full Inorganic portion map. Portion hub: Inorganic · Inorganic analysis.

Syllabus on this page is topic-scoped: p-Block Elements (Groups 13–18). The parent portion (Inorganic) also covers other topics — use the portion hub for the full map.

Must cover (this topic)

OS and reactivity trends groups 13–17; anomalies of B,C,N,O,F
Group 13–18 compounds and reactions as listed (borax, diborane, silicones, NH₃/HNO₃, O₃/H₂SO₄, Cl₂/HCl, Xe compounds, etc.)

Gaps / watch-outs

No topic-specific exclusions flagged — finish the unit points below for p-Block.

Source: https://jeeadv.ac.in/documents/jee-advanced-2026-syllabus.pdf

Unit 01

p-Block Elements (Groups 13–18)

high

Exam focusAnomalies of B,C,N,O,F; key compounds per group in syllabus list.

Syllabus points

OS and reactivity trends groups 13–17; anomalies of B,C,N,O,F
Group 13–18 compounds and reactions as listed (borax, diborane, silicones, NH₃/HNO₃, O₃/H₂SO₄, Cl₂/HCl, Xe compounds, etc.)

Do / check

One A4 sheet per group: prep–properties–uses

Full Chemistry syllabus →

2020–2026 paper weight

Trends · why this topic matters

Topic match inside parent portion Inorganic (23.7% of Chemistry tags). Stats below are portion backdrop; matched subtopics show where p-Block Elements (Groups 13–18) sits.

Portion share23.7%

TrendStable

Study intensityCore · weekly

Avg / year8.14

This topic in papers

p-block — 4 tagged (7% of Inorganic)21:125:126:2

Portion-wide type/difficulty mix lives on the Inorganic analysis — not repeated here so this page stays on p-Block.

Full PCM trends board → · Inorganic subject page →

Cross-topic stems

Mixed joins for this topic

Advanced rarely asks a chapter in isolation. These are tagged multi-idea Chemistry stems that touch p-Block Elements (Groups 13–18) — practise the knowledge bridge, not only the single-chapter drill.

Chemistry2026 · Paper 2 · Q17–Q18linked-numerical

Kjeldahl nitrogen + Carius sulphur on related organics

Organic practical – Kjeldahl+Organic practical – Carius+Stoichiometric estimation

Knowledge bridge

Step 1: from structure/formula of L, count N and convert mass to moles of NH₃, then to mL of 1 M H₂SO₄. Step 2: from M, count S and convert to grams of BaSO₄ via Carius stoichiometry. Step 3: keep atomic masses consistent across both linked estimation asks.

Why it feels hard

NCERT ‘end chapter’ methods under numerical pressure; easy arithmetic slips.

What to practise

Treat Kjeldahl/Carius as fixed stoichiometry templates — practise until automatic.

2026 year review →Chemistry notes →Quick card →Syllabus →

Chemistry2026 · Paper 2 · Q3–Q4multi-concept

Polymer ozonolysis + biomolecule sweetener

Polymers – natural rubber+Ozonolysis / functional tests+Biomolecules – disaccharide

Knowledge bridge

Step 1: ozonolyse the rubber repeating unit to carbonyl fragments; apply iodoform/Tollens to identify Y. Step 2: read the chlorinated disaccharide sweetener as linked galactose+fructose-type units. Step 3: connect ‘polymer degradation products’ thinking with biomolecule structure reading.

Why it feels hard

Students often skip polymers/biomolecules until too late; stems assume NCERT fluency.

What to practise

Schedule polymers + carbohydrates every fortnight with one Adv-style product ID set.

2026 year review →Chemistry notes →Quick card →Syllabus →

All mixed joins →

Why methods matter

Common methods that change your score

Structures and oxidation states organize the many reactions and exceptions of p-block chemistry.

Group-state ladder

Inert-pair trends become visible.

Do thisWrite maximum OS and the state two units lower.

Why it works

Inert-pair trends become visible.

See it once

Tl(I), Pb(II), and Bi(III) gain stability down their groups.

First-member filter

Explains most top-of-group anomalies.

Do thisFor B/C/N/O/F test small size, no d orbitals, and strong pπ–pπ bonding.

Why it works

Explains most top-of-group anomalies.

See it once

N cannot form NCl₅; P can form PCl₅.

Structure before property

Prevents formula-based guesses.

Do thisCount electron pairs/bridges before deciding shape or polarity.

Why it works

Prevents formula-based guesses.

See it once

B₂H₆ contains two 3c–2e B–H–B bridges.

Condition-tag equations

p-block products often change with conditions.

Do thisAttach hot/cold, dilute/concentrated, and aqueous/excess labels.

Why it works

p-block products often change with conditions.

See it once

Hot concentrated alkali gives chlorate, not hypochlorite.

Processed examples

Sample questions · full working

Read the impact line first. Then notice which family/model was chosen. The solution is written the way your rough sheet should look in the hall.

bankFamily · Structure and electron deficiency

Sample question

How many three-centre two-electron bonds occur in B₂H₆?

This stem rewards early recognition of the structure and electron deficiency model.

Model chosenUse the diborane bridge model.

Processed solution

Diborane contains four terminal B–H bonds.
Two hydrogens bridge the boron atoms.
Each B–H–B bridge is a 3c–2e bond.
Therefore there are two.

Answer2

Takeaway: Bridging hydrogens diagnose electron-deficient bonding.

standardFamily · Oxoacid strength and redox

Sample question

Order HClO, HClO₂, HClO₃ and HClO₄ by acid strength.

This stem rewards early recognition of the oxoacid strength and redox model.

Model chosenCompare terminal oxygen stabilization.

Processed solution

All acids have the same central atom.
Additional terminal oxygens withdraw electron density.
They also delocalize conjugate-base charge.
Order: HClO<HClO₂<HClO₃<HClO₄.

AnswerHClO<HClO₂<HClO₃<HClO₄

Takeaway: More terminal oxygen generally strengthens comparable oxoacids.

twistFamily · Disproportionation and hydrolysis

Sample question

Balance the disproportionation of Cl₂ in hot concentrated OH⁻ to chloride and chlorate.

This Advanced-level variation couples hidden constraints with the disproportionation and hydrolysis model.

Model chosenBalance simultaneous Cl(0)→Cl(−1) and Cl(+5).

Processed solution

Reduction to Cl⁻ gains one electron per chlorine.
Oxidation to ClO₃⁻ loses five electrons per chlorine.
Thus five reduced Cl atoms accompany one oxidized Cl atom.
Supply six Cl₂-derived atoms and balance O/H in base.
3Cl₂+6OH⁻→5Cl⁻+ClO₃⁻+3H₂O.

Answer3Cl₂+6OH⁻→5Cl⁻+ClO₃⁻+3H₂O

Takeaway: Disproportionation coefficients follow electron exchange.

Reusable models

Common question families

Advanced stems cluster. Name the family in 10–15s, write the fast model, then run the same path. Do not invent a new plan each time.

Structure and electron deficiency

Looks likeBoranes, halides, oxoacids or hypervalent molecules

Fast modelCount electrons and identify multicentre bonds or expanded coordination.

Same solve path

Draw the skeletal structure.
Count valence electrons.
Locate bridges/lone pairs/π bonds.
Infer shape and reactivity.

Rough skeleton

skeleton
electron count
bonding

Why faster

Recognition fixes the model before arithmetic begins.

Refuse this

Do not start blind expansion or casework before identifying the governing model.

Oxoacid strength and redox

Looks likeAcidity, basicity or oxidizing power of p-block oxoacids

Fast modelCompare oxidation state, non-OH oxygens and conjugate-base stabilization.

Same solve path

Draw comparable structures.
Count terminal =O groups.
Assess oxidation-state accessibility.
Rank the requested property.

Rough skeleton

structures
=O/O.S.
order

Why faster

Recognition fixes the model before arithmetic begins.

Refuse this

Do not start blind expansion or casework before identifying the governing model.

Disproportionation and hydrolysis

Looks likeHalogen, phosphorus or sulphur compound in water/alkali

Fast modelTrack one element into simultaneous oxidation and reduction products.

Same solve path

Assign initial oxidation state.
Identify stable products in the stated medium.
Balance electron changes.
Balance atoms and charge.

Rough skeleton

O.S.
products
balanced equation

Why faster

Recognition fixes the model before arithmetic begins.

Refuse this

Do not start blind expansion or casework before identifying the governing model.

Preparations and qualitative reactions

Looks likeNamed industrial/laboratory process or characteristic test

Fast modelUse the smallest reaction network linking feed to product.

Same solve path

Identify the key intermediate.
Write essential conditions.
Balance the conversion.
Attach the diagnostic observation.

Rough skeleton

feed/intermediate
conditions
product/test

Why faster

Recognition fixes the model before arithmetic begins.

Refuse this

Do not start blind expansion or casework before identifying the governing model.

Hall timing

45–75s process

0–12s
Classify the stem and underline the species, condition, and demanded comparison.
Decide whether the controlling idea is trend, structure, equilibrium, redox, or a named preparation/test.
12–25s
Write the governing configuration, equation, or exception before inspecting options.
Fix oxidation state, charge balance, medium, and periodic position; do not answer from a vague trend.
25–60s
Apply the shortest valid model and eliminate statements one clause at a time.
For multi-correct questions, independently verify every species and every condition.
60–75s
Audit charge, atoms, trend direction, colour/state, and syllabus exceptions.
Reject conclusions that silently change medium, coordination number, temperature, or oxidation state.

After the model is locked

Quick formula bank

Borax bead hydrolysis

B₄O₇²⁻ + 7H₂O ⇌ 4H₃BO₃ + 2OH⁻

Explain alkaline borax solution.

Diborane hydrolysis

B₂H₆ + 6H₂O → 2H₃BO₃ + 6H₂

Hydride reactivity and gas yield.

Haber process

N₂ + 3H₂ ⇌ 2NH₃; Fe catalyst, high p

Equilibrium/industrial-condition questions.

Ostwald core

4NH₃ + 5O₂ → 4NO + 6H₂O (Pt/Rh)

Nitric-acid manufacture.

Ozone iodometry

O₃ + 2I⁻ + 2H⁺ → O₂ + I₂ + H₂O

Oxidising character/estimation.

Contact core

2SO₂ + O₂ ⇌ 2SO₃ (V₂O₅)

Sulfuric-acid manufacture.

Chlorine disproportionation

Cl₂ + 2OH⁻(cold,dil.) → Cl⁻ + ClO⁻ + H₂O

Medium/temperature-sensitive products.

XeF₂ hydrolysis

2XeF₂ + 2H₂O → 2Xe + 4HF + O₂

Xenon-compound reaction questions.

Mental bank

B₂H₆ has four terminal and two bridging H.
Boric acid is Lewis-monobasic in water.
NH₃ basicity reflects lone-pair availability.
O₃ is bent, diamagnetic, and a strong oxidant.
H₂SO₄ is dehydrating; hot concentrated acid is oxidising.
Cl₂ disproportionates in alkali.
XeF₂ linear, XeF₄ square planar, XeF₆ distorted octahedral.
Silicones have –Si–O–Si– backbones.
B₂H₆: 4 terminal + 2 bridging H
Boric acid is Lewis-monobasic in water
XeF₂ linear; XeF₄ square planar
Cl₂ disproportionates in alkali

Make it automatic

Practice · checklist

Daily

Revise one p-block structure and reaction map from memory.
Solve 6 mixed single/multiple-correct statements.
Balance or justify two reactions without notes.

Weekly

Attempt one 25-minute p-block structure and reaction set.
Rebuild the exception/colour/reagent sheet.
Redo every error after hiding the answer.

100% checklist

Know first-member anomalies for Groups 13–17.
Can rank common oxidation-state stabilities.
Draw structures of listed hydrides/interhalogens/xenon fluorides.
Recall key industrial reaction conditions.
Balance hydrolysis and disproportionation equations.
Can solve statement sets without guessing from group trends alone.
First-member anomaly flagged when relevant
Key structures drawable with correct geometry
Oxidation-state stability tied to inert-pair / bond energy