Group 14 elements: the carbon family

What are the group 14 elements?

In plain words: the group runs from carbon, the backbone of every living thing, through the silicon of rocks and computer chips, to the soft metals tin and lead. All have four outer electrons. The light ones share all four; lead, at the bottom, prefers to use only two.

Scope: measured trends below concern C–Pb, not the little-studied synthetic flerovium. Oxidation state is formal bookkeeping and must be distinguished from valency and coordination number.

No 2026–27 NCERT textbook has a chapter on the p-block; the JEE Main 2027 and NEET (UG) 2026 syllabuses list it in Unit 10. This page covers group 14: configuration, oxidation states, trends, properties and the anomaly of carbon. Facts and data from beyond the NCERT books are labelled with their source.

Electronic configuration ns^² np^² and oxidation states

• The configurations follow the aufbau order (NCERT Class 11 Chemistry, Unit 2).
• +4, the group valence. With four valence electrons the group shows +4, as in SiCl₄ (NCERT Class 11 Chemistry, page 241) and in the dioxides CO₂ to PbO₂. The group also forms tetrahydrides CH₄, SiH₄, GeH₄ and SnH₄, but their formula alone does not fix oxidation state: carbon is −4 in CH₄, whereas silicon is +4 in SiH₄ under the usual electronegativity assignment (formulas: NCERT Class 11 Chemistry, Table 3.9, page 93; oxidation states reasoned from Pauling electronegativities).
• +2 grows more stable down the group. Germanium is mostly +4, though many +2 compounds are known (Wikipedia, “Germanium”). Tin has two main states, +2 and the slightly more stable +4 (Wikipedia, “Tin”). Lead compounds are usually +2; few inorganic lead(IV) compounds are known, though organolead compounds are mostly lead(IV), and even fluorine and chlorine give only PbF₂ and PbCl₂ with the metal (Wikipedia, “Lead”).
• So tin(II) is a reducing agent, turning into tin(IV): 2HgCl₂ + SnCl₂ → Hg₂Cl₂ + SnCl₄ (NCERT Class 11 Chemistry, page 236). Lead(IV) is an oxidising agent, turning into lead(II): PbO₂ oxidises the Cl⁻ of hydrochloric acid to chlorine (NCERT Class 11 Chemistry, page 246).
• Carbon can be −4, as in methane and in the methanide carbides: carbon alone forms monatomic anions, C⁴⁻, while the other members form Zintl ions with electropositive metals such as magnesium (Wikipedia, “Carbon group”). So the group is not restricted to +2 and +4 (reasoned).

Atomic radius, ionisation enthalpy and electronegativity down the group

Covalent radius in pm, first ionisation enthalpy Δ_iH₁ in kJ mol⁻¹, and electronegativity (EN) on the Pauling scale:

Radii follow the Pyykkö–Atsumi molecular single-bond scale (2009), and ionisation enthalpies are rounded atomic data; electronegativities use the stated Pauling table. All three are as tabulated in the Wikipedia data pages “Atomic radii of the elements”, “Molar ionization energies of the elements” and “Electronegativities of the elements”, the data pages cited below. NCERT’s Class 11 tables give C 77 pm and 2.5, Si 117 pm and 1.8 (NCERT Class 11 Chemistry, Tables 3.6 and 3.8, pages 86 and 91).

• Atomic radius rises down the group, as each member adds a shell (NCERT Class 11 Chemistry, page 86). The rise is small from Si to Ge, where ten 3d electrons are added, and from Sn to Pb, where fourteen 4f electrons are added: these inner electrons shield the nucleus poorly (reasoned; the lanthanoid contraction, NCERT Class 12 Chemistry Part I, Unit 4, page 93).
• Ionisation enthalpy falls sharply from C to Si, then slowly, but lead’s is a little above tin’s: 716 against 709 kJ mol⁻¹ (data page). The poorly shielding 4f electrons and relativistic effects, which contract lead’s 6s and 6p orbitals, are the cause (Wikipedia, “Lead”).
• Electronegativity falls from C to Si and then changes little. The values for lead depend on the table and on its oxidation state: the data page gives 2.33, while its Lange column gives 1.8 (Wikipedia data page); 2.33 is lead(IV)’s value and lead(II)’s is 1.87 (Wikipedia, “Lead”). In an exam, the safe trend is: carbon is the most electronegative member.

Physical properties

Melting and boiling points in K, density in g cm⁻³:

Values from the Wikipedia data pages for melting points, boiling points (CRC values) and densities; at standard pressure carbon sublimes, near 3825 °C (Wikipedia, “Carbon group”).

• Metallic character increases down the group (NCERT Class 11 Chemistry, page 84): non-metal C and metalloids Si and Ge (NCERT Class 11 Chemistry, page 85), metals Sn and Pb (Wikipedia, “Carbon group”).
• Melting and boiling points fall down the group, though lead melts a little higher than tin (Wikipedia, “Carbon group”). Carbon, silicon and germanium are giant covalent networks with diamond-type or layered structures (Wikipedia, “Carbon group”), held by strong bonds, which is why they melt so high (reasoned).
• Density increases down the group (Wikipedia, “Carbon group”).
• Allotropes. Carbon has several: graphite, diamond, fullerenes, graphene and amorphous carbon. Tin has two: silvery β-tin, and grey, powdery α-tin, which forms below 13.2 °C; the conversion can be slow, but tin objects in the cold can eventually crumble, “tin pest” (Wikipedia, “Carbon group”).

Chemical properties: oxides, reactivity towards water, and halides; the inert pair effect

• Oxides. All form dioxides, MO₂ (NCERT Class 11 Chemistry, Table 3.9, page 93); carbon, germanium, tin and lead also form monoxides (Wikipedia, “Carbon group”, “Germanium” and “Lead(II) oxide”).
  • CO₂ and SiO₂, oxides of a non-metal and a metalloid, are acidic: most non-metals give acidic oxides (NCERT Class 10 Science, Chapter 3, page 40). Silicon dioxide reacts with bases under some conditions (Wikipedia, “Silicon dioxide”).
  • CO is a neutral oxide, with neither acidic nor basic properties (NCERT Class 11 Chemistry, page 94), and a reducing agent: hot CO reduces tin ore, SnO₂ + 2CO → Sn + 2CO₂ (Wikipedia, “Tin(IV) oxide”).
  • SnO₂ is amphoteric in Wikipedia’s “Tin” and in the opening of “Tin(IV) oxide”, though slow to react: it dissolves in sulphuric acid and in molten sodium hydroxide, while solutions of acid or base hardly attack it (Wikipedia, “Tin(IV) oxide”, which in its Reactions section also says it is not amphoteric). Amphoterism describes reaction types, not rapid dissolution in every solution (reasoned). In an exam, call SnO₂ amphoteric.
  • PbO is amphoteric: it reacts with both acids and bases (Wikipedia, “Lead(II) oxide”). In its problem on Pb₃O₄, NCERT calls PbO a basic oxide, which is how it behaves towards acids (NCERT Class 11 Chemistry, page 246). PbO₂, like PbO, can form plumbate anions with bases (Wikipedia, “Lead”).
  • So the oxides grow less acidic and more basic down the group (reasoned).
• Water. Hot carbon (coke) reacts with steam to give water gas, a mixture of CO and H₂ (Wikipedia, “Water gas”): C + H₂O → CO + H₂. Silicon is relatively unreactive (Wikipedia, “Silicon”), and germanium is not attacked by dilute acids or alkalis (Wikipedia, “Germanium”). Tin resists corrosion by water (Wikipedia, “Tin”); NCERT gives it as a metal that does not react with steam but does give hydrogen with acids (NCERT Class 11 Chemistry, page 243). NCERT Class 10 Science says lead does “not react with water at all” (page 43); give that in an exam. Beyond the NCERT text: in moist air it can gain a protective surface layer, but its corrosion and dissolution in water depend on oxygen, pH and other dissolved species (Wikipedia, “Lead”).
• Halides. Carbon and silicon form tetrahalides with all the halogens. Germanium and tin form both dihalides and tetrahalides; lead forms dihalides, but its tetrabromide and tetraiodide are unstable (Wikipedia, “Carbon group”). The lead(IV) halides grow less stable from fluoride to iodide: PbF₄ is stable, though less so than PbF₂; PbCl₄, a yellow oil, decomposes at room temperature; PbBr₄ is less stable still; and PbI₄ may not exist. PbO₂ oxidises chloride in hydrochloric acid while Pb(IV) is reduced to Pb(II); the net equation does not establish a PbCl₄ intermediate (Wikipedia, “Lead”).
• Hydrolysis of the tetrachlorides. SiCl₄ fumes in moist air and reacts readily with water: SiCl₄ + 2H₂O → SiO₂ + 4HCl. Carbon tetrachloride is not readily hydrolysed (Wikipedia, “Silicon tetrachloride”). In an exam, give the reason from NCERT page 93: silicon can expand its valence shell to take a lone pair from water, carbon cannot (reasoned from NCERT Class 11 Chemistry, page 93). Beyond the NCERT text: SiCl₄ reacts in two steps through a five-coordinate silicon intermediate, while CCl₄ could react only in one step with a very large activation energy, so it is kinetically resistant (International Chemistry Olympiad 2021, preparatory problem 14); the bonding involves little d-orbital participation (Reed and Schleyer, JACS, 1990; Wikipedia, “Hypervalent molecule”).
• The inert pair effect. Down the group the two ns electrons, poorly shielded by the d and f electrons in between, take less part in bonding, so +2 grows more stable (Wikipedia, “Inert-pair effect”; NCERT Class 12 Chemistry Part I, Section 4.3.4, page 97). This explains why lead(IV) is oxidising and tin(II) is reducing, and why PbI₄ and PbBr₄ are unstable (reasoned).

Anomalous behaviour of carbon

Carbon differs from the rest of the group because it is small, has a high electronegativity and has only four valence orbitals (NCERT Class 11 Chemistry, page 93).

• Maximum covalency 4. With only 2s and 2p orbitals, carbon can form at most four bonds, while silicon, with nine valence orbitals including 3d, can expand its valence shell (NCERT Class 11 Chemistry, page 93); give that reason in an exam. Beyond the NCERT text: modern bonding analyses find little d-orbital participation in such compounds (Reed and Schleyer, JACS, 1990; Wikipedia, “Hypervalent molecule”). Silicon gives [SiF₆]²⁻, as hexafluorosilicic acid, H₂SiF₆, when HF attacks silica (Wikipedia, “Silicon dioxide”).
• Multiple bonds. Carbon readily forms pπ–pπ multiple bonds, to itself (C=C, C≡C) and to other period 2 elements (C=O, C≡N) (NCERT Class 11 Chemistry, page 93). So CO₂ is a small linear molecule and a gas, while SiO₂ is a three-dimensional network solid in which each silicon is bonded to four oxygens (Wikipedia, “Silicon dioxide”).
• Catenation. Carbon links to itself in long chains and rings far more readily than any other element, which is why there are so many organic compounds. The tendency falls down the group, as the bonds between like atoms grow weaker (Wikipedia, “Catenation”).
• Inert halides. CCl₄ is not readily hydrolysed, while SiCl₄ is (Wikipedia, “Silicon tetrachloride”).
• Carbon forms methanide carbides and has the highest ionisation enthalpy and electronegativity in the group (data table above).

Solved examples

Common mistakes to avoid

Quick revision summary

• Group 14: C, Si, Ge, Sn, Pb (and Fl); valence configuration ns^² np^²; C non-metal, Si and Ge metalloids, Sn and Pb metals.
• Oxidation states +4 and +2; +2 grows more stable down the group (inert pair effect): Pb(IV) oxidises, Sn(II) reduces.
• Radius rises down the group, only a little from Si to Ge and from Sn to Pb; ionisation enthalpy falls, but Pb is above Sn.
• Oxides grow more basic down the group: CO_₂ and SiO_₂ are acidic, SnO_₂ and PbO amphoteric; CO is a neutral oxide.
• Carbon is anomalous: maximum covalency 4, multiple bonds, catenation, CO_₂ a molecule, CCl_₄ not hydrolysed.

Questions students ask

What is the oxidation state of lead in Pb₃O₄?

Lead in Pb₃O₄ has an average oxidation state of +8/3, from 3x + 4(−2) = 0, but NCERT lists Pb₃O₄ among the mixed oxides whose fractional oxidation numbers are averages over atoms in different states (NCERT Class 11 Chemistry, Unit 7, page 245). This red lead behaves as 2PbO·PbO₂ (page 246; Example 1), two Pb(II) to one Pb(IV), and (2 × 2 + 4)/3 = 8/3. Beyond the NCERT text, its structure is lead(II) orthoplumbate(IV), (Pb²⁺)₂[PbO₄]⁴⁻ (Wikipedia, “Lead(II,IV) oxide”).

Why are group 14 elements called the carbon family, and what are their other names?

Group 14 is called the carbon family after its first member, carbon, as groups 13 and 15 are the boron and nitrogen families (reasoned). NCERT’s periodic table also marks it IVA, the older notation that IUPAC’s numbering of groups 1 to 18 replaced (NCERT Class 11 Chemistry, Unit 3, pages 78–79). Beyond the NCERT text, it is also called the tetrels, from the Greek tetra, four, for its four valence electrons and the numeral IV, and sometimes the crystallogens; the old European label was IVB, and semiconductor physics still speaks of group IV (Wikipedia, “Carbon group”).

What is the order of ionisation enthalpy and electronegativity in group 14?

On the Wikipedia data in the page’s table, the first ionisation enthalpy order in group 14 is C > Si > Ge > Pb > Sn (1087, 787, 762, 716 and 709 kJ mol^⁻¹), lead edging above tin because the filled 4f shell and relativistic effects hold its 6p electrons more tightly (Wikipedia, “Lead”). Electronegativity has no agreed order below carbon: the table’s Pauling values give C > Pb > Ge > Sn > Si (2.55, 2.33, 2.01, 1.96, 1.90), with lead’s 2.33 being its value as lead(IV), while the Allen scale gives C > Ge > Si > Pb > Sn (Wikipedia, “Electronegativities of the elements” and “Lead”). Carbon comes first on every scale.

Why is SnCl₄ a liquid while SnCl₂ is a solid?

SnCl₄ is a liquid and SnCl₂ a solid because tin(IV), twice as charged as tin(II), polarises chloride more and bonds covalently: by Fajans’ rules, “the greater the charge on the cation, the greater the covalent character” (NCERT Class 11 Chemistry, Unit 4, page 112). Beyond the NCERT text, SnCl₄ is made of separate molecules, boiling at 114 °C, while solid SnCl₂, melting at 247 °C, forms chloride-bridged chains (Wikipedia, “Tin(IV) chloride”, “Tin(II) chloride”). Lead too: PbCl₄ is a yellow oil, PbCl₂ melts at 501 °C (Wikipedia, “Lead(IV) chloride”, “Lead(II) chloride”).

Are the allotropes of carbon in the JEE Main 2027 and NEET (UG) 2026 syllabus?

The allotropes of carbon are not named in the JEE Main 2027 or the NEET (UG) 2026 syllabus: Unit 10, p-Block Elements, gives groups 13 to 18 only a general introduction (configuration, trends and the first element’s unique behaviour), and no unit of either names diamond, graphite or fullerenes. The hybridisation of carbon in diamond and graphite is answered on the tetravalence of carbon page, and the p-block syllabus as a whole on the group 13 page.

Practice questions

Try each question first, then open the answer to check your working.

1. Q1. Why is SnCl₂ a reducing agent while PbO₂ is an oxidising agent?

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   Down group 14 the +2 state grows more stable (inert pair effect). Tin is slightly more stable as +4, so Sn(II) is readily oxidised to Sn(IV): SnCl₂ reduces. Lead is more stable as +2, so Pb(IV) is readily reduced to Pb(II): PbO₂ oxidises (Wikipedia, “Tin” and “Lead”; NCERT Class 11 Chemistry, page 246).

2. Q2. Why is CO₂ a gas while SiO₂ is a high-melting solid?

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   Carbon forms strong pπ–pπ double bonds with oxygen, so CO₂ is a small separate molecule held to its neighbours only by weak forces. Ordinary bulk silica favours a network rather than separate SiO₂ molecules; each Si is singly bonded to four O atoms in a giant network, so melting SiO₂ means breaking strong covalent bonds (NCERT Class 11 Chemistry, page 93; Wikipedia, “Silicon dioxide”).

3. Q3. Write the electronic configuration of lead and its usual oxidation state.

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   Pb: [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p². Its usual oxidation state is +2: only the two 6p electrons are used, while the 6s pair stays unshared (Wikipedia, “Lead”).