🗓️How to Study — Your 5-Day Plan
Class 11 p-Block is half memory, half logic. Group trends can be reasoned; specific compounds (diborane, silicones, allotropes) must be recalled. This 5-day plan splits them: two days for concepts and trends, two days for named compounds, one day for the chapter test.
📌 The one rule that unlocks Groups 13-14
- The inert-pair effect is the single unifying concept for both groups. Down each group, the ns² electrons become increasingly reluctant to participate in bonding → lower oxidation state becomes more stable. Group 13: +3 → +1 (Tl⁺ is stable, Tl³⁺ is a strong oxidiser). Group 14: +4 → +2 (Pb²⁺ is stable, Pb⁴⁺ is a strong oxidiser; PbCl₄ decomposes, PbCl₂ stable). Master this and half the chapter's questions become instant.
📚Topic Map — 2 Groups, 14 Blocks
Every NEET question comes from one of these 14 blocks. 🔥 count = typical frequency across recent NEET papers.
13Group 13 — Boron Family (B · Al · Ga · In · Tl)
Group 13 trends down the family
- Configuration: ns² np¹ · 3 valence electrons.
- Atomic radius: B (85 pm) < Ga (135 pm) < Al (143 pm). Ga is smaller than Al — an anomaly caused by poor shielding of newly-added 3d electrons.
- Ionisation enthalpy: generally decreases down, but with the Ga anomaly.
- Electronegativity: decreases B → Al, then remains roughly constant.
- Metallic character: B is a non-metal; Al, Ga, In, Tl are all metals. B is a metalloid.
- Melting point: B very high (~2100 °C) · Al ~660 °C · Ga anomalously low (~30 °C — liquid on a warm day) · In ~157 °C · Tl ~304 °C.
Why boron behaves differently
- Very small size + no d-orbitals → max covalency = 4 (never 5 or 6).
- Non-metallic character — the only non-metal in the group.
- Forms only covalent compounds (never ionic, unlike Al, Ga, In, Tl which readily give M³⁺).
- Exhibits diagonal relationship with silicon (Group 14): both form covalent polymeric oxides, weak acidic oxides, and stable hydrides.
- BX₃ compounds are electron-deficient (6 e⁻ around B) → strong Lewis acids.
Inert-pair effect (Group 13)
- Down the group, the ns² pair becomes increasingly reluctant to participate in bonding (poor shielding by intervening d/f electrons → more strongly held).
- +3 stability decreases down; +1 stability increases down.
- Tl mostly +1: Tl⁺ is highly stable, resembling K⁺/Rb⁺ (similar radius). Tl³⁺ is a strong oxidising agent.
- Stability order: TlCl (stable) > TlCl₃ (unstable, decomposes to TlCl + Cl₂). Reverse of AlCl (unknown) vs AlCl₃ (very stable).
Borax (Na₂B₄O₇·10H₂O)
- Structure: the B₄O₇²⁻ anion contains 2 BO₃ (trigonal) + 2 BO₄ (tetrahedral) units — not 4 equivalent B atoms.
- Correct structural formula: Na₂[B₄O₅(OH)₄] · 8H₂O.
- On heating, first loses water → anhydrous borax → melts to a clear glass containing sodium metaborate + boric anhydride: Na₂B₄O₇ →Δ→ 2NaBO₂ + B₂O₃
- Borax bead test: hot bead of B₂O₃ dissolves oxides of transition metals to form coloured metaborates. Classic: Cu → blue-green, Cr → green, Co → deep blue, Fe → yellow-brown, Mn → violet.
Orthoboric acid H₃BO₃ — the Lewis-acid trick
- Structure: planar sheets of BO₃ units connected by H-bonds → soft, soapy feel.
- NOT a Bronsted acid (doesn't donate H⁺). Instead, it accepts OH⁻ from water: H₃BO₃ + 2H₂O ⇌ [B(OH)₄]⁻ + H₃O⁺
- Since only one proton is released per H₃BO₃ (from the water it consumes), boric acid is monobasic — not tribasic despite the "H₃" formula.
- Weak acid: Ka ≈ 5.8 × 10⁻¹⁰.
- Uses: antiseptic (eye wash), in Pyrex glass, enamels.
- On heating: H₃BO₃ → HBO₂ (metaboric acid) at 100 °C → B₂O₃ + H₂O (boric anhydride) at higher T.
Diborane B₂H₆ — the banana-bond structure
- Structure: two BH₂ units bridged by 2 hydrogens. Each B is sp³. Two terminal H per B (regular 2c-2e σ bonds) + two bridging H.
- The bridging bonds are 3-centre-2-electron (3c-2e) — one pair of electrons spread over B-H-B. Also called "banana bonds" due to their curved shape.
- 12 valence electrons total in B₂H₆: 4 terminal B-H bonds × 2 e⁻ = 8, plus 2 bridging bonds × 2 e⁻ = 4. Total 12. ✓
- Preparation: 3 LiAlH₄ + 4 BF₃ → 2 B₂H₆ + 3 LiF + 3 AlF₃. Or 2 NaBH₄ + I₂ → B₂H₆ + 2 NaI + H₂.
- Reactivity: spontaneously catches fire in air (highly exothermic). Reacts with NH₃ → borazine B₃N₃H₆ ("inorganic benzene").
AlCl₃ and its dimer Al₂Cl₆
- Solid AlCl₃: layered lattice, partly ionic.
- Vapour (below 800°C): exists as dimer Al₂Cl₆ (edge-sharing tetrahedra). Two bridging Cl → each Al is 4-coordinated.
- Above 800°C: dissociates to monomeric AlCl₃ (planar, sp², electron-deficient).
- Lewis acid — accepts a lone pair from ligands like Cl⁻, NH₃, RCl. This is why AlCl₃ catalyses Friedel-Crafts reactions (accepts Cl⁻ from RCl to generate R⁺).
- BF₃: monomer in all states (F too small to bridge). Also a strong Lewis acid — accepts a lone pair (e.g. from NH₃) to form BF₃·NH₃ adduct.
🧮Interactive Inert-Pair Effect Explorer
Pick any element from Groups 13 or 14 — the explorer tells you its most stable oxidation state, the reason, and the practical NEET consequence. Great for the "same element, opposite behaviour" traps (Pb²⁺ vs Pb⁴⁺, Sn²⁺ vs Sn⁴⁺, Tl⁺ vs Tl³⁺).
📈Interactive Periodic Trends
Pick a group and a property — see how the value changes as you walk down the column. Perfect for spotting the "kinks" NEET loves to test (Ga smaller than Al · Al IE lower than B · Pb slightly more EN than Sn).
14Group 14 — Carbon Family (C · Si · Ge · Sn · Pb)
Group 14 trends down the family
- Configuration: ns² np² · 4 valence electrons.
- Atomic radius: C (77) < Si (117) < Ge (122) < Sn (140) < Pb (146) pm.
- Metallic character: increases down. C/Si non-metals · Ge metalloid · Sn/Pb metals.
- Electronegativity: C (2.5) > Si (1.8) ≈ Ge ≈ Sn (1.8) · Pb slightly higher (1.9) — inert-pair anomaly.
- Oxidation states: +4 dominant for C, Si, Ge. +2 becomes progressively more stable down; Pb²⁺ >> Pb⁴⁺ in stability due to inert-pair effect.
Why carbon behaves differently
- Small size + high EN + no d-orbitals → forms strong pπ-pπ multiple bonds (C=C, C≡C, C=O). Other Group 14 elements prefer only single bonds.
- Catenation ability: C can form chains and rings of virtually unlimited length. Reason: C-C bond enthalpy is very high (355 kJ/mol) — higher than Si-Si (222) or Ge-Ge (188).
- This is why organic chemistry exists — C is the only element that can build the immense variety of molecules seen in life.
- Max covalency = 4 (no d-orbitals to expand).
Catenation trend across the group
C >> Si > Ge ≈ Sn >> Pb — the ability of an element to bond to itself.
| Bond | Enthalpy (kJ/mol) | Consequence |
|---|---|---|
| C-C | 355 | Very strong · virtually unlimited chains + rings |
| Si-Si | 222 | Modest · silicon chains break easily · silicones use Si-O-Si backbone instead |
| Ge-Ge | 188 | Weak |
| Sn-Sn | 151 | Very weak |
| Pb-Pb | ~100 | Almost non-existent |
Allotropes of Carbon
| Allotrope | Hybridisation | Structure | Properties |
|---|---|---|---|
| Diamond | sp³ | 3D tetrahedral · every C bonded to 4 others | Hardest natural material · non-conductor · high refractive index |
| Graphite | sp² | 2D layers of fused hexagons · layers held by van der Waals | Conducts electricity (delocalised π) · soft (layers slide) · pencil lead + lubricant |
| Fullerene (C₆₀) | sp² | Soccer-ball · 20 hexagons + 12 pentagons · 60 C atoms | Only pure allotrope (diamond and graphite always contain impurities/defects). Semi-conductor. |
| Carbon nanotubes | sp² | Rolled-up graphite sheets | Immense tensile strength |
NEET traps: "Diamond is a good conductor" — FALSE (non-conductor). "Graphite is soft because it has weak C-C bonds" — FALSE (soft because layers slide; in-layer bonds are strong). "Fullerene has both hexagons and pentagons" — TRUE (12 pentagons + 20 hexagons).
Oxides of carbon
- CO: linear (sp hybridised on C). Contains a triple bond (2π + 1σ). Colourless, odourless, extremely toxic — binds Fe of haemoglobin ~200× stronger than O₂.
- CO is a strong reducing agent: reduces Fe₂O₃ → Fe in blast furnace.
- CO is a neutral oxide (doesn't react with acids or bases at ordinary temperatures).
- CO₂: linear (O=C=O, sp on C, no lone pair). Acidic oxide — forms carbonic acid with water. Greenhouse gas.
- Carbides: ionic (CaC₂ = calcium acetylide, gives C₂H₂ with water) · covalent (SiC = carborundum, extremely hard) · interstitial (WC, cementite in steel).
Silicates, silicones, zeolites
Silicates: based on the SiO₄⁴⁻ tetrahedron (sp³ Si, 4 O at corners). Silicate types depend on how tetrahedra share corners:
| Type | Sharing | Example |
|---|---|---|
| Ortho- (isolated) | None | Zircon ZrSiO₄ |
| Pyro- (dimer) | 1 corner | Thortveitite Sc₂Si₂O₇ |
| Cyclic | 2 corners | Beryl Be₃Al₂[Si₆O₁₈] |
| Chain (single) | 2 corners | Pyroxenes |
| Sheet (2D) | 3 corners | Talc, mica |
| 3D framework | 4 corners | Quartz (SiO₂), feldspar |
Silicones: synthetic polymers with a Si-O-Si backbone and organic R groups. General formula (R₂SiO)_n. Water-repellent, thermally stable, biocompatible. Used in medical implants, waterproofing sprays, greases.
Zeolites: microporous 3D aluminosilicates. Cavities (~500 pm) act as molecular sieves. Uses: cracking of petroleum (ZSM-5), ion exchange, dehydration.
SiC (carborundum): covalent 3D network like diamond. Extremely hard — used as abrasive.
Tin and Lead — the inert-pair drama
- SnCl₂: solid, ionic Sn²⁺(Cl⁻)₂. Powerful reducing agent (Sn²⁺ → Sn⁴⁺). Reduces HgCl₂ to Hg₂Cl₂ (white) → Hg (grey/black) — the "tin-mirror" test.
- SnCl₄: covalent molecule (like CCl₄), fuming liquid. Sn⁴⁺ is not a reducer.
- PbCl₂: stable ionic solid. Pb²⁺.
- PbCl₄: covalent, unstable — decomposes to PbCl₂ + Cl₂ (Pb⁴⁺ is a strong oxidiser). Inert-pair effect showing.
- PbO₂: powerful oxidising agent (Pb⁴⁺ → Pb²⁺). Reacts with hot conc. HCl to give Cl₂ + PbCl₂ + H₂O.
- Litharge (PbO): yellow. Red lead (Pb₃O₄): 2 PbO · PbO₂ — mixed oxide. When heated it releases O₂ due to instability of Pb⁴⁺.
📈Graphs Every NEET Aspirant Must Recognise
1 · Atomic radius trend in Group 13 (Ga anomaly)
Ga is smaller than Al — reason: after Al, the 3d subshell fills across the transition series before Ga. The 3d electrons shield the nuclear charge poorly, so Ga's outer electrons feel a stronger effective nuclear pull → contracted.
2 · Stability: +3 vs +1 oxidation states (inert-pair effect · Group 13)
Down the group: +3 stability decreases (green) · +1 stability increases (orange). Tl mostly exists as Tl⁺; Tl³⁺ is a strong oxidiser (unstable). Same pattern in Group 14 for +4 vs +2 (Pb²⁺ is stable, Pb⁴⁺ oxidises).
3 · Catenation ability (Group 14 bond enthalpy)
C-C bond is exceptionally strong (355 kJ/mol), which is why organic chemistry (and life) exists. Down the group, bond enthalpy drops sharply → catenation ability declines. Pb barely bonds to itself.
4 · Diborane B₂H₆ — bridging structure
B₂H₆ has 4 terminal H (2 per B, regular σ bonds) and 2 bridging H forming 3-centre-2-electron banana bonds. Total 12 valence electrons: 4 terminal bonds × 2e + 2 bridging bonds × 2e = 12 ✓.
5 · Al₂Cl₆ dimer structure
Al₂Cl₆ in vapour: two tetrahedra share an edge (2 bridging Cl atoms). Each Al is sp³. This solves Al's electron deficiency in monomeric AlCl₃ (which is sp², only 6 e⁻ around Al). At > 800°C, the dimer dissociates back to monomeric AlCl₃.
6 · Diamond (sp³ 3D) vs Graphite (sp² 2D)
Diamond: every C is sp³ · 4 tetrahedral bonds · rigid 3D lattice · no free electrons → non-conductor · hardest natural material. Graphite: every C is sp² · 3 bonds in-plane · delocalised π-electron above/below sheet → conducts · sheets slide → soft, lubricates.
⚡Shortcuts & Memory Tricks (15)
Down Group 13: +1 more stable. Down Group 14: +2 more stable. Consequence: Tl⁺ stable, Tl³⁺ oxidises; Pb²⁺ stable, Pb⁴⁺ oxidises. Same story, different group.
H₃BO₃ is MONOBASIC, not tribasic. It's a Lewis acid — accepts OH⁻ from water, releases only 1 H⁺ per boric-acid molecule. Guaranteed NEET question.
B₂H₆ has 12 valence electrons: 4 terminal B-H × 2e + 2 bridging B-H-B × 2e (3c-2e each) = 12. Each bridging bond uses 2 electrons but spans 3 atomic centres.
AlCl₃ dimerises to Al₂Cl₆ because Al accepts bridging Cl. BF₃ stays monomeric because F is too small to bridge — no dimer.
Ga is smaller than Al (135 pm vs 143 pm) — because Ga follows the first transition series (poor d-shielding). Same reason Ge is small in Group 14.
Cu = blue-green · Co = deep blue · Fe = yellow-brown · Cr = green · Mn = violet. Coloured metaborates on the hot borax bead. Asked in NEET most years.
Ga melts at ~30 °C — it liquefies in the palm of your hand. Uses: thermometers (Ga replaces mercury), GaAs semiconductors.
B (Group 13) and Si (Group 14) show diagonal relationship: covalent polymeric oxides, hydrides, similar electronegativity. Explains why B is metalloid-like even though it's Group 13.
C >> Si. C-C bond enthalpy 355 kJ/mol vs Si-Si 222. This is why C makes organic chemistry possible and Si can't. Silicon backbones use Si-O-Si instead (silicones, silicates).
Diamond: NON-conductor (all e⁻ locked in sp³ σ bonds). Graphite: CONDUCTS (delocalised π e⁻ in each sheet). Classic reversed-expectation NEET trap.
C₆₀ = 20 hexagons + 12 pentagons. Only pure allotrope of carbon (diamond/graphite always contain defects). Semiconductor.
CO₂ = linear (sp on C · O=C=O). Common wrong guess: bent (like H₂O). C has no lone pair → no bending. But SO₂ and O₃ are bent (central atom has a lone pair).
SnCl₂ = ionic solid · reducing agent (Sn²⁺ → Sn⁴⁺). SnCl₄ = covalent liquid · not a reducer. Same element, opposite roles by oxidation state.
Because Pb⁴⁺ is unstable (inert-pair effect), PbCl₄ → PbCl₂ + Cl₂ on heating. Meanwhile SnCl₄ is perfectly stable (Sn⁴⁺ still acceptable). Down-group instability of +4.
Corners shared by SiO₄ tetrahedra: 0 = ortho, 1 = pyro, 2 = chain/cyclic, 3 = sheet, 4 = 3D framework (quartz). Structure follows the sharing rule.
⚠️Exceptions & NEET Traps
The 12 exceptions NEET returns to again and again
- H₃BO₃ is monobasic, not tribasic. It doesn't donate H⁺ directly — it accepts OH⁻ from water. Lewis acid, not Bronsted.
- Ga is smaller than Al (poor 3d shielding after Al in the transition series).
- Ga melts at 30 °C — liquid on a warm day. Anomalously low melting point.
- Diamond is a non-conductor of electricity despite being pure carbon; graphite conducts. Reason: e⁻ localisation in sp³ vs sp².
- Graphite is soft despite strong C-C in-plane bonds — layers slide over each other via weak van der Waals.
- BF₃ does not dimerise (F too small to bridge); AlCl₃ readily dimerises to Al₂Cl₆.
- Boric acid is planar layer, held together by H-bonds — that's why it's soapy/greasy.
- Diborane has bridging H atoms in 3c-2e "banana" bonds — no direct B-B bond exists.
- CO₂ is linear, not bent (no lone pair on C).
- SnCl₂ is ionic and reducing but SnCl₄ is covalent and non-reducing — same element, opposite bonding and role.
- PbCl₄ decomposes on heating to PbCl₂ + Cl₂ — inert-pair effect makes Pb⁴⁺ unstable.
- Red lead (Pb₃O₄) is a mixed oxide = 2PbO · PbO₂. Contains both +2 and +4 lead.
🔥Most-Asked NEET Topics (Frequency-Ranked)
Based on frequency across recent NEET/AIPMT papers. Top 5 give ~ 70% of the chapter's questions.
| Rank | Topic | Frequency | Specific angles NEET uses |
|---|---|---|---|
| 1 | Diborane B₂H₆ structure | 🔥🔥🔥🔥🔥 · almost every year | Number of 3c-2e bonds · bridging vs terminal H · electron count · hybridisation of B |
| 2 | Inert-pair effect (both groups) | 🔥🔥🔥🔥 · 1-2/yr | Why TlCl > TlCl₃ · why PbCl₄ decomposes · Sn²⁺ vs Sn⁴⁺ |
| 3 | Boric acid — nature + reactions | 🔥🔥🔥🔥 · 1/yr | Monobasic Lewis acid · reaction with NaOH · layered structure |
| 4 | Allotropes of C | 🔥🔥🔥🔥 · 1-2/yr | Diamond sp³ non-conductor · graphite sp² conductor · fullerene C₆₀ |
| 5 | Catenation trend | 🔥🔥🔥 · 1/yr | C >> Si > Ge > Sn > Pb · reason (bond enthalpy) |
| 6 | AlCl₃ dimer + Lewis-acid character | 🔥🔥🔥 · 1/yr | Al₂Cl₆ in vapour · sp³ Al · Friedel-Crafts catalyst mechanism |
| 7 | Borax structure + bead test | 🔥🔥🔥 · 1/yr | Na₂[B₄O₅(OH)₄]·8H₂O · 2 BO₃ + 2 BO₄ · metal-oxide bead colours |
| 8 | Silicones, silicates, zeolites | 🔥🔥🔥 · 1/yr | Silicone R₂SiO chain · silicate corner-sharing rules · zeolite as cracking catalyst |
| 9 | Tin/Lead chlorides (SnCl₂/₄, PbCl₂/₄) | 🔥🔥 · every 2 yrs | SnCl₂ reducing · PbCl₄ decomposes · PbO₂ oxidising |
| 10 | Anomalous behaviour of B, C | 🔥🔥 · every 2 yrs | No d-orbitals · pπ-pπ bonds · diagonal relationships |
🎯Assertion-Reason Practice Bank
10 NEET-style drills. Both statements may be true — you must decide whether R correctly explains A.
Answer + explanation
Answer + explanation
Answer + explanation
Answer + explanation
Answer + explanation
Answer + explanation
Answer + explanation
Answer + explanation
Answer + explanation
Answer + explanation
⭐Cheat Sheet Dashboard
Scan these golden rules first — they answer most multiple-choice traps at a glance. Read before Day 1, revisit before Day 5 test.
Scan these golden rules first — they answer most multiple-choice traps.
Group 13 — Boron Family
B, Al, Ga, In, Tl · outer config ns² np¹ · common oxidation state +3.
Heavier elements (In, Tl) prefer the +1 state — inert pair effect. B is a non-metal (covalent); the rest are metals.
Group 14 — Carbon Family
C, Si, Ge, Sn, Pb · outer config ns² np² · common oxidation state +4; heavier prefer +2.
Catenation order: C ≫ Si > Ge ≈ Sn ≫ Pb. C–C bonds form long chains; Pb²⁺ dominant due to inert pair.
Anomalous Behaviour (B & C)
The first member of each group stands apart — small size, high IE/EN, and no d-orbitals.
So B can't expand octet (max BF₄⁻, no BF₆³⁻); C forms strong p–p multiple bonds (CO₂, alkenes/alkynes) — Si prefers single bonds and gives 3-D SiO₂.
Inert Pair Effect
Down a group, the outer ns² electrons increasingly stay put (poor shielding by d/f electrons → high penetration).
⇒ Heavier elements show a stable oxidation state 2 less than the group state: Tl⁺ and Pb²⁺ are the most stable. Pb⁴⁺ is a strong oxidiser; Sn²⁺ is a strong reducer.
Diagonal Relationship
Li↔Mg, Be↔Al, B↔Si — similar size & polarising power across a diagonal.
So B (Group 13) and Si (Group 14) both form covalent polymeric oxides, weak acidic oxides, and stable hydrides — not behaviour you'd expect from groupmates alone.
🧪Quick Reactions & Key Compounds
The handful of reactions that account for most NEET questions on this chapter. Memorise the right-hand side.
The handful of reactions and structures that account for most NEET questions on this chapter. Memorise the right-hand side.
🧠Must-Memorise — for Aamirah
1Group Configurations & Character
- Group 13 (B, Al, Ga, In, Tl): ns² np¹ · common +3 · B is non-metal, rest metals; Tl⁺ most stable.
- Group 14 (C, Si, Ge, Sn, Pb): ns² np² · common +4 · C non-metal, Si/Ge metalloids, Sn/Pb metals; Pb²⁺ most stable.
- Metallic character increases down both groups.
2Trend Orders (memorise verbatim)
- 1st IE — Group 13: B > Tl > Ga > Al > In (not monotonic!)
- Atomic radius — Group 13: Tl > In > Al > Ga > B (Ga < Al kink)
- Atomic radius — Group 14: Pb > Sn > Ge > Si > C
- 1st IE — Group 14: C > Si > Ge > Pb > Sn (Pb > Sn due to f-shielding)
- Electronegativity (Group 14): C ≫ Si ≈ Ge ≈ Sn < Pb (C highest by far)
3Acidity Orders
- Lewis acidity of BX₃: BF₃ < BCl₃ < BBr₃ < BI₃ (back-bonding from F weakens BF₃).
- Group 13 oxides: B₂O₃ acidic → Al₂O₃, Ga₂O₃ amphoteric → In₂O₃, Tl₂O₃ basic.
- Group 14 oxides: CO₂, SiO₂ acidic · GeO₂ weakly acidic · SnO, PbO amphoteric · SnO₂, PbO₂ amphoteric.
- Boric acid H₃BO₃ is a monobasic Lewis acid (accepts OH⁻, doesn’t donate H⁺).
4Catenation & Bond Strengths
- Catenation: C ≫ Si > Ge ≈ Sn ≫ Pb.
5Hybridisation Cheat-Sheet
6Key Compounds & Their Formulas
Na₂B₄O₇·10H₂OH₃BO₃ or B(OH)₃B₂H₆B₃N₃H₆SiCSiO₂CO + N₂CO + H₂Pb₃O₄2PbCO₃·Pb(OH)₂7Inert-Pair Trio (oxidiser vs reducer)
- Oxidising agents: Tl³⁺, Pb⁴⁺ (PbO₂, PbCl₄, Pb₃O₄) — they want to drop back to Tl⁺ / Pb²⁺.
- Reducing agents: Sn²⁺ (SnCl₂), Ga⁺ — they want to climb to Sn⁴⁺ / Ga³⁺.
- Most stable +1 in Group 13 → Tl⁺. Most stable +2 in Group 14 → Pb²⁺.
- Order of inert-pair effect: C < Si < Ge < Sn < Pb.
- Thermal stability: PbCl₂ > PbBr₂ > PbI₂; PbCl₂ > PbCl₄.
8Anomalies & “Doesn’t Exist”
- BF₆³⁻ does NOT exist — B has no d-orbitals (max coord. = 4).
- SiF₆²⁻ exists; CF₆²⁻ does NOT (Si has 3d-orbitals).
- CO₂ is a gas; SiO₂ is a 3-D solid (no p–π in Si).
- B³⁺ cation does NOT exist — B forms covalent bonds (high IE, small size).
- Only C in Group 14 forms p–p multiple bonds readily (C=C, C≡C, C=O).
- Anhydrous AlCl₃ exists as Al₂Cl₆ dimer (in water, as [Al(H₂O)₆]³⁺).
- HF attacks glass: SiO₂ + 4HF → SiF₄ + 2H₂O.
- Boric acid is monobasic and Lewis, not Brønsted.
9Numbers Worth Memorising
10Reactions to Recall in One Line
- BF₃ + 3H₂O → H₃BO₃ + 3HF (hydrolysis)
- B₂H₆ + 6H₂O → 2H₃BO₃ + 6H₂
- 3B₂H₆ + 6NH₃ → 2B₃N₃H₆ + 12H₂ (borazine)
- Al + NaOH + H₂O → NaAlO₂ + H₂↑ (amphoteric Al)
- 2Al + 6HCl → 2AlCl₃ + 3H₂↑
- SiO₂ + 4HF → SiF₄ + 2H₂O
- Si + 2NaOH + H₂O → Na₂SiO₃ + 2H₂
- n Me₂SiCl₂ + n H₂O → (Me₂SiO)n + 2n HCl (silicone)
- SnCl₂ + 2HgCl₂ → SnCl₄ + Hg₂Cl₂ (Sn²⁺ reducer)
📚Solved Problems — Worked Examples
15 stepwise problems covering the whole chapter. Each card has an easy explanation (what's really being asked), a full solution, and a one-line final answer. Click to expand.
🃏Quick-Recall Flashcards
12 flashcards for spaced-recall drilling. Tap any card to flip and see the answer. Cover the whole chapter — the fastest way to check retention before a test.
🎯Final Checklist Before Chapter Test
- ☐ Inert-pair effect explains Tl⁺ > Tl³⁺ (Group 13) and Pb²⁺ > Pb⁴⁺ (Group 14)?
- ☐ H₃BO₃ is monobasic (Lewis mechanism, not O-H count) — recalled cold?
- ☐ Diborane B₂H₆: 4 terminal + 2 bridging H · 3c-2e banana bonds · 12 valence e⁻?
- ☐ Al₂Cl₆ dimer (edge-sharing tetrahedra) · BF₃ stays monomer (F too small)?
- ☐ Ga smaller than Al (poor d-shielding) — this anomaly ready?
- ☐ Borax structure = 2 BO₃ + 2 BO₄ (not 4 equivalent B) + bead-test colours?
- ☐ Diamond sp³ non-conductor · graphite sp² conductor · fullerene C₆₀ (20 hex + 12 pent)?
- ☐ Catenation order C >> Si > Ge > Sn > Pb + reason (bond enthalpy)?
- ☐ CO₂ linear (sp on C, no lp) · CO reducer + poisonous?
- ☐ Silicone R₂SiO water-repellent · zeolite as cracking catalyst?
- ☐ SnCl₂ reducing agent · SnCl₄ covalent Lewis acid · PbO₂ powerful oxidiser?
- ☐ Diagonal relationship B ↔ Si (covalent oxides + hydrides)?
All 12 ticked → NEET-pace for Class 11 p-Block. Any 3+ unchecked → repair before Day 5 test.