75 free MCQs on p-Block Elements (Groups 13 & 14) with worked answers and explanations. Covers the Boron family (Group 13: B, Al) and the Carbon family (Group 14: C, Si, Ge, Sn, Pb). Key topics include Lewis acid behaviour of BF₃, borax bead test, silicates, silicones, allotropes of carbon, and trends in properties down the group.
Take the timed p-Block Elements (Groups 13 & 14) chapterwise test →Below are 75 practice questions on p-Block Elements (Groups 13 & 14), sorted Easy → Hard. Tap “Show answer & explanation” under any question to check yourself. Want the full theory first? Read the p-Block Elements (Groups 13 & 14) notes.
Diamond's rigid 3D tetrahedral network makes it the hardest natural material, while graphite's flat hexagonal sheets are held together only by weak forces, letting them slide past each other (used as a lubricant and in pencils).
Q1.
The first member of each p-block group differs from the rest chiefly because it:
Answer: A. Has a small size, high electronegativity and no d-orbitals in its valence shell
Why: The first element (e.g., B, C) is small, more electronegative and lacks valence d-orbitals, so it shows anomalous behaviour compared with the heavier members of its group.
Q2.
Why does boron always form covalent compounds rather than the B<sup>3+</sup> ion?
Answer: B. The sum of its first three ionisation enthalpies is very high
Why: Removing three electrons from small boron needs a very large amount of energy, so forming B<sup>3+</sup> is not favoured; boron bonds covalently instead.
Q3.
Which of the following correctly lists a property that increases down Group 14 from C to Pb?
Answer: C. Metallic character
Why: Down Group 14 the elements change from non-metallic carbon to metallic lead, so metallic character increases while catenation and electronegativity decrease.
Q4.
Carbon shows a maximum covalency of four whereas silicon can expand it to six (as in SiF<sub>6</sub><sup>2-</sup>). This is because silicon:
Answer: D. Has accessible vacant 3d-orbitals
Why: Silicon has empty 3d-orbitals that can accept additional electron pairs, allowing a covalency of six; carbon has no d-orbitals in its valence shell and is limited to four.
Q5.
Which statement about inert pair effect in Group 13 is correct?
Answer: A. The +1 state becomes more stable down the group, Tl<sup>+</sup> being quite stable
Why: Due to the inert pair effect the ns<sup>2</sup> electrons become reluctant to bond down the group, so the +1 state grows in stability and Tl<sup>+</sup> is more stable than Tl<sup>3+</sup>.
Q6.
Which groups make up the p-block?
Answer: A. Groups 13 to 18
Why: The p-block consists of Groups 13 through 18, where the outermost electrons enter p orbitals.
Q7.
Aluminium (Group 13) forms a thin oxide layer that makes it:
Answer: A. Corrosion-resistant (passive)
Why: Al reacts with O<sub>2</sub> to form a thin Al<sub>2</sub>O<sub>3</sub> layer that protects the metal from further corrosion (passivation).
Q8.
Graphite is a good conductor of electricity because:
Answer: A. Delocalised pi electrons in the layers are free to move
Why: In graphite, each C is sp<sup>2</sup> hybridised; the unhybridised p electrons form delocalised pi bonds along the layers, enabling electrical conductivity.
Q9.
Which is the most abundant metal in the Earth’s crust?
Answer: D. Aluminium
Why: Aluminium (about 8.3% by mass) is the most abundant metal in the Earth’s crust; oxygen and silicon are the most abundant elements overall.
Q10.
Diamond and graphite are allotropes of which Group 14 element?
Answer: A. Carbon
Why: Both diamond (sp³) and graphite (sp²) are allotropic forms of carbon; fullerene (C₆₀) is a third.
Q11.
The characteristic group oxidation state of the Group 13 elements is:
Answer: C. +3
Why: Group 13 elements have the ns²np¹ configuration, giving a group oxidation state of +3.
Q12.
Which gas is released when aluminium reacts with dilute hydrochloric acid?
Answer: A. Hydrogen
Why: 2Al + 6HCl → 2AlCl₃ + 3H₂ - aluminium displaces hydrogen from the acid.
Q13.
Group 13 of the periodic table is also known as the:
Answer: B. boron family
Why: Group 13 (B, Al, Ga, In, Tl) is called the boron family.
Q14.
Group 14 of the periodic table is also known as the:
Answer: B. carbon family
Why: Group 14 (C, Si, Ge, Sn, Pb) is called the carbon family.
Q15.
The only non-metal in Group 13 is:
Answer: B. boron
Why: Boron is a metalloid/non-metal; the rest of Group 13 are metals.
Q16.
The general electronic configuration of Group 14 elements is:
Answer: B. ns²np²
Why: Group 14 elements have two electrons in the outermost p subshell: ns²np².
Q17.
Which Group 14 element is the second most abundant element in the Earth’s crust?
Answer: B. silicon
Why: Silicon (about 27% by mass) is the second most abundant element in the crust, after oxygen.
Q18.
Graphite conducts electricity well because it possesses:
Answer: A. delocalised free electrons
Why: Each carbon in graphite uses three of its four valence electrons in bonding, leaving one delocalised electron per atom to carry current.
Q19.
In diamond, each carbon atom is covalently bonded to how many other carbon atoms?
Answer: C. four
Why: Diamond has a three-dimensional network in which every carbon is bonded to four others, making it extremely hard.
Q20.
The most important ore of aluminium is:
Answer: B. bauxite
Why: Bauxite (hydrated aluminium oxide) is the chief ore from which aluminium is extracted.
Q21.
At room temperature, carbon dioxide is a gas whereas silicon dioxide is a:
Answer: B. solid
Why: CO₂ is a discrete molecular gas, but SiO₂ forms a giant covalent solid network.
Q22.
Which allotrope of carbon is soft and used as a lubricant?
Answer: B. graphite
Why: Graphite’s layers slide over one another easily, making it a good solid lubricant.
Q23.
The oxidation state that becomes increasingly stable on going down Group 14 is:
Answer: B. +2
Why: Owing to the inert-pair effect, the +2 state grows more stable down the group (Pb²⁺ is very stable).
Q24.
Producer gas is a fuel mixture of carbon monoxide and:
Answer: B. nitrogen
Why: Producer gas is mainly CO and N₂, made by passing air over red-hot coke.
Q25.
Which Group 14 element is the basis of most semiconductor devices?
Answer: B. silicon
Why: Silicon is the standard semiconductor material used in chips and transistors.
Q26.
Diborane is described as electron-deficient. The two bridging B–H–B linkages are best described as:
Answer: C. Three-centre two-electron (banana) bonds
Why: In B<sub>2</sub>H<sub>6</sub> the four terminal B–H bonds are normal 2c-2e bonds, while the two bridges are three-centre two-electron (banana) bonds, explaining its electron deficiency.
Q27.
Assertion: Anhydrous aluminium chloride exists as a dimer Al<sub>2</sub>Cl<sub>6</sub> in the vapour and non-polar solvents. Reason: Dimerisation lets each aluminium complete its octet through chlorine bridges.
Answer: D. Both assertion and reason are true and the reason explains the assertion
Why: Monomeric AlCl<sub>3</sub> has only a sextet on Al; by dimerising through chloride bridges each Al attains an octet, so dimer formation is driven by octet completion.
Q28.
Carbon monoxide is a powerful reducing agent used in metallurgy. In the reaction Fe<sub>2</sub>O<sub>3</sub> + 3CO → 2Fe + 3CO<sub>2</sub>, the carbon in CO:
Answer: A. Is oxidised from +2 to +4
Why: CO reduces the iron oxide to iron; the carbon itself goes from +2 in CO to +4 in CO<sub>2</sub>, so it is oxidised while acting as the reducing agent.
Q29.
On warming, the +2 compound SnCl<sub>2</sub> reduces mercuric chloride. This reaction is possible because tin in the +2 state:
Answer: B. Tends to be oxidised to the more stable +4 state, so it is a reducing agent
Why: For tin the +4 state is more stable than +2, so Sn(II) readily loses two electrons to become Sn(IV), acting as a reducing agent (e.g., reducing HgCl<sub>2</sub> to Hg<sub>2</sub>Cl<sub>2</sub> and then Hg).
Q30.
Down Group 14, the stability of the +2 oxidation state relative to +4:
Answer: B. increases
Why: Because of the inert-pair effect, the +2 state becomes more stable down the group (Pb²⁺ is more stable than Pb⁴⁺).
Q31.
BF₃ behaves as a Lewis acid because it has:
Answer: C. an empty orbital and incomplete octet
Why: Boron in BF₃ has only six electrons and a vacant 2p orbital, so it accepts an electron pair - the definition of a Lewis acid.
Q32.
How many bridging hydrogen atoms are present in a molecule of diborane (B₂H₆)?
Answer: B. 2
Why: Diborane has two B–H–B bridges (three-centre two-electron bonds) and four terminal B–H bonds.
Q33.
The tendency of an element to link with itself forming long chains, strongest in carbon, is called:
Answer: D. catenation
Why: Catenation is self-linking of atoms; carbon’s strong C–C bonds make it the champion, which underlies organic chemistry.
Q34.
Aluminium oxide (Al₂O₃) is amphoteric, meaning it reacts:
Answer: C. with both acids and bases
Why: Being amphoteric, Al₂O₃ dissolves in acids (forming Al³⁺ salts) and in alkalis (forming aluminates).
Q35.
Silicones are synthetic polymers built on a backbone of alternating:
Answer: A. silicon and oxygen atoms
Why: Silicones have an –Si–O–Si–O– backbone with organic groups on silicon, giving water-repellent, heat-stable materials.
Q36.
Boric acid, H₃BO₃, is a weak monobasic acid because it:
Answer: D. accepts OH⁻ from water
Why: Boric acid is a Lewis acid: B(OH)₃ + H₂O → [B(OH)₄]⁻ + H⁺, so it produces H⁺ by accepting OH⁻ rather than donating a proton.
Q37.
Boron does not readily form a B³⁺ ion because of its:
Answer: B. high ionisation energy
Why: The very high total ionisation energy needed to remove three electrons makes ionic B³⁺ compounds unfavourable.
Q38.
Borax has the chemical formula:
Answer: A. Na₂B₄O₇·10H₂O
Why: Borax is sodium tetraborate decahydrate, Na₂B₄O₇·10H₂O.
Q39.
The hybridisation of each carbon atom in diamond is:
Answer: C. sp³
Why: Every carbon in diamond forms four single bonds, so it is sp³ hybridised.
Q40.
The hybridisation of each carbon atom in graphite is:
Answer: B. sp²
Why: Carbon in graphite forms three sigma bonds in a plane, so it is sp² hybridised.
Q41.
Carbon monoxide is highly poisonous because it:
Answer: B. binds tightly to haemoglobin
Why: CO binds to haemoglobin about 200 times more strongly than O₂, blocking oxygen transport.
Q42.
Silicones are water-repellent (hydrophobic) because they carry:
Answer: B. non-polar alkyl groups
Why: The organic alkyl groups on the silicon–oxygen backbone are non-polar, making silicones water-repellent.
Q43.
Aluminium is chosen for overhead electrical cables because it is:
Answer: B. a light, good conductor
Why: Aluminium combines low density with good electrical conductivity, ideal for transmission lines.
Q44.
The increasing stability of the +1 oxidation state down Group 13 is explained by the:
Answer: B. inert-pair effect
Why: The inert-pair effect - reluctance of the ns² electrons to bond - makes the lower (+1) state more stable down the group.
Q45.
Which of these oxides is amphoteric?
Answer: B. Al₂O₃
Why: Al₂O₃ reacts with both acids and bases, so it is amphoteric; B₂O₃, CO₂ and SiO₂ are acidic.
Q46.
Carbon shows far more catenation than silicon because:
Answer: B. C–C bonds are stronger
Why: The strong C–C bond lets carbon form long stable chains and rings, the basis of organic chemistry.
Q47.
Dry ice is the solid form of:
Answer: B. carbon dioxide
Why: Dry ice is solid CO₂, which sublimes directly to a gas without melting.
Q48.
When carbon dioxide is passed through lime water, the white precipitate formed is:
Answer: B. calcium carbonate
Why: CO₂ + Ca(OH)₂ → CaCO₃ (white) + H₂O, the classic test for carbon dioxide.
Q49.
Silicon carbide (carborundum) is widely used as an:
Answer: B. abrasive
Why: Silicon carbide is nearly as hard as diamond and is used as an abrasive for grinding and cutting.
Q50.
The compound borazine (B₃N₃H₆) is often called:
Answer: A. inorganic benzene
Why: Borazine is isoelectronic and isostructural with benzene, earning it the name inorganic benzene.
Q51.
The order of Lewis acid strength of the boron trihalides is BF<sub>3</sub> < BCl<sub>3</sub> < BBr<sub>3</sub>. The accepted explanation is that:
Answer: C. Back-bonding into boron's empty 2p-orbital is strongest in BF<sub>3</sub> and weakest in BBr<sub>3</sub>
Why: p-p back-bonding from halogen to boron is most effective for the small, well-matched F (2p), partially satisfying boron's electron deficiency; it weakens down to Br, so BBr<sub>3</sub> is the strongest Lewis acid.
Q52.
When borax is heated strongly it first swells and then yields a transparent glassy bead. The bead, used in the borax bead test, consists essentially of:
Answer: D. Sodium metaborate and boric anhydride (NaBO<sub>2</sub> and B<sub>2</sub>O<sub>3</sub>)
Why: On heating, borax loses water and then melts to a glassy bead of sodium metaborate and boric anhydride (NaBO<sub>2</sub>.B<sub>2</sub>O<sub>3</sub>), which dissolves coloured metal oxides to give characteristic colours.
Q53.
Carbon dioxide is a discrete linear molecule and a gas, while silicon dioxide is a hard high-melting solid. The fundamental reason is that:
Answer: A. Carbon forms p-p multiple bonds (O=C=O); silicon forms single Si–O network bonds
Why: Small carbon forms effective p-p pi bonds, allowing discrete O=C=O molecules; silicon forms weak pi bonds so it satisfies its valences with single Si–O sigma bonds in a three-dimensional network solid.
Q54.
Thallium(I) iodide and thallium(III) iodide differ in a subtle way: TlI<sub>3</sub> is actually thallium(I) triiodide rather than thallium(III) iodide. This is best explained by the fact that:
Answer: B. Tl<sup>3+</sup> is a strong enough oxidant to oxidise I<sup>-</sup>, so the stable species is Tl<sup>+</sup> with I<sub>3</sub><sup>-</sup>
Why: Because of the inert pair effect Tl<sup>3+</sup> is a strong oxidiser; it would oxidise I<sup>-</sup> to iodine, so the compound exists as Tl<sup>+</sup>(I<sub>3</sub>)<sup>-</sup>, i.e., thallium(I) triiodide.
Q55.
Aluminium reacts with both dilute HCl and aqueous NaOH to liberate dihydrogen, showing that Al<sub>2</sub>O<sub>3</sub> and Al are amphoteric. With excess hot NaOH the aluminium-containing product is:
Answer: C. Sodium tetrahydroxoaluminate(III), Na[Al(OH)<sub>4</sub>]
Why: Aluminium dissolves in hot NaOH giving sodium tetrahydroxoaluminate(III), Na[Al(OH)<sub>4</sub>], with evolution of H<sub>2</sub>, illustrating its amphoteric character.
Q56.
Boron trifluoride (BF<sub>3</sub>) is a Lewis acid but its Lewis acidity is less than BCl<sub>3</sub>. This is because:
Answer: A. F's lone pair back-donation into B's empty p orbital reduces electron deficiency more than Cl
Why: F is a better pi-donor than Cl (smaller, better size match with B 2p); back-bonding in BF<sub>3</sub> partially fills B's vacant orbital more effectively, reducing Lewis acidity.
Q57.
Silicones (polysiloxanes) are used in high-temperature applications because:
Answer: A. Si-O bonds are stronger than C-C bonds due to partial ionic character and high bond energy
Why: Si-O bond energy is ~450 kJ/mol (very strong); silicone polymers maintain stability at temperatures that would degrade organic polymers.
Q58.
Fullerene C<sub>60</sub> (Buckminsterfullerene) consists of:
Answer: A. 20 hexagons and 12 pentagons in a soccer ball arrangement
Why: C<sub>60</sub> has exactly 20 hexagonal and 12 pentagonal faces; the pentagonal faces prevent infinite flat-sheet growth, curving it into a sphere.
Q59.
Carbon exists as diamond (sp<sup>3</sup>) and graphite (sp<sup>2</sup>). The allotrope graphene is:
Answer: A. A single layer of graphite with exceptional electrical, mechanical, and thermal properties
Why: Graphene is a single-atom-thick honeycomb lattice of sp<sup>2</sup> carbon; it is the strongest material and has the highest electron mobility known.
Q60.
The correct order of stability of the +2 oxidation state for Ge, Sn and Pb is:
Answer: B. Pb > Sn > Ge
Why: The inert-pair effect strengthens down the group, so the +2 state is most stable for lead: Pb > Sn > Ge.
Q61.
Anhydrous AlCl₃ exists as the dimer Al₂Cl₆, in which each aluminium attains:
Answer: A. an octet using chlorine bridges
Why: Two chlorine atoms bridge the aluminiums, donating lone pairs so each Al completes its octet in the dimeric Al₂Cl₆ structure.
Q62.
Diborane (B₂H₆) is termed an electron-deficient molecule because it has:
Answer: B. too few electrons for its normal bonds
Why: Diborane lacks enough electrons for eight ordinary bonds, so it uses two three-centre two-electron B–H–B bridges.
Q63.
The three-centre two-electron (banana) bond is a feature of:
Answer: B. diborane
Why: The bridging B–H–B links in diborane are three-centre two-electron bonds.
Q64.
On descending Group 14 from carbon to lead, the metallic character:
Answer: B. increases
Why: Metallic character increases down the group: carbon is a non-metal, silicon and germanium metalloids, tin and lead metals.
Q65.
Tin exists mainly in the ___ state, whereas lead is more stable in the ___ state:
Answer: B. +4 and +2
Why: Tin favours +4, but by the inert-pair effect the heavier lead is more stable as +2.
Q66.
The reaction of aluminium with hot aqueous sodium hydroxide produces:
Answer: B. sodium aluminate and hydrogen
Why: 2Al + 2NaOH + 2H₂O → 2NaAlO₂ + 3H₂; aluminium dissolves in alkali, showing its amphoteric nature.
Q67.
In the giant covalent structure of silica (SiO₂), each silicon atom is bonded to:
Answer: C. four oxygens
Why: Each Si is tetrahedrally bonded to four oxygen atoms, and each oxygen bridges two silicons.
Q68.
A molecule of fullerene (C₆₀) has a cage shape resembling a:
Answer: B. a football-like cage
Why: C₆₀ is a closed cage of 20 hexagons and 12 pentagons, shaped like a football.
Q69.
The most stable oxidation state of carbon in the vast majority of its compounds is:
Answer: B. +4
Why: Carbon most commonly shows the +4 oxidation state (as in CO₂ and organic compounds).
Q70.
Anhydrous AlCl₃ is a covalent dimer, but when dissolved in water it behaves as:
Answer: B. an ionic electrolyte
Why: In water AlCl₃ ionises to give hydrated Al³⁺ and Cl⁻ ions, so the solution conducts electricity.
Q71.
Alumina dissolves in both acids and alkalis, which shows that it is:
Answer: B. amphoteric
Why: Reacting with both acids (forming Al³⁺ salts) and alkalis (forming aluminates) is the defining property of an amphoteric oxide.
Q72.
Gallium is unusual among metals because it:
Answer: B. melts in the warmth of a hand
Why: Gallium melts at about 30 °C, so it will liquefy in the warmth of a hand.
Q73.
Lead pipes are avoided for carrying drinking water because lead is:
Answer: B. toxic to humans
Why: Dissolved lead is a cumulative poison, so lead plumbing is unsafe for drinking water.
Q74.
Silicones are used as sealants, water-proofing agents and lubricants because of their:
Answer: B. heat stability and water repellence
Why: Their inert silicon–oxygen backbone gives silicones heat resistance, chemical inertness and water repellence.
Q75.
The relative stability of the +4 oxidation state among Group 14 elements follows the order:
Answer: B. Si > Ge > Sn > Pb
Why: The +4 state becomes less stable down the group as the inert-pair effect strengthens, so stability of +4 runs Si > Ge > Sn > Pb.