Ch 11The p-Block Elements — Class 11 Chemistry, concept-first.

Group 13 consists of boron (B), aluminium (Al), gallium (Ga), indium (In) and thallium (Tl). This is one of the most chemically diverse groups in the periodic table — boron behaves as a typical non-me…

Every Group 13 element has the same outer (valence) configuration, . But their inner cores are progressively more complicated on descending the group, and it is this hidden complexity — not the visibl…

Going down any group, an extra electron shell is added at each step, so atomic radius is expected to grow steadily. Group 13 mostly follows this rule — except at gallium.

If Group 13 followed the simple periodic rule, ionisation enthalpy would fall smoothly all the way down the group as atomic size increases. It does not.

Electronegativity in Group 13 does not fall monotonically down the group. It decreases from boron to aluminium, but then, instead of continuing to fall for gallium, indium and thallium, it rises again…

Boron stands apart from the rest of the group. It is a non-metal — an extremely hard, black solid that exists in several allotropic forms, held together by a very strong covalent crystal lattice.

Oxidation states and the inert-pair effect. Boron is so small that the sum of its first three ionisation enthalpies is enormous — far too costly for boron to simply lose three electrons and form a bar…

Boron, as the first (and smallest) member of Group 13, behaves quite differently from the rest of its group — a pattern the NCERT syllabus repeats for the first member of several p-block groups.

Boron forms a wide range of compounds, but three of them carry the most weight in the NCERT syllabus and in industrial chemistry: borax (), orthoboric acid (), and diborane ().

Borax is the single most important compound of boron. It is a white crystalline solid usually written as , but this formula is a simplification: the real species present is the tetranuclear anionic un…

Orthoboric acid is a white, crystalline solid with a distinctly soapy feel. It is only sparingly soluble in cold water but dissolves much more readily in hot water.

Diborane is the simplest known boron hydride.

Boron and its compounds. Boron is extremely hard, refractory, of low density and very low electrical conductivity — a combination that gives it several specialised uses.

Group 14, the carbon family, comprises carbon (C), silicon (Si), germanium (Ge), tin (Sn) and lead (Pb).

Every Group 14 element shares the outer valence configuration . But, exactly as in Group 13, the inner core is not the same across the group — moving from carbon down to lead, heavier members pick up…

Covalent radius increases sharply between carbon and silicon — the first two members — but the further increase from silicon down through germanium, tin and lead is comparatively small.

Every Group 14 element has a higher first ionisation enthalpy than the corresponding Group 13 element — a direct consequence of Group 14's smaller atomic size and extra nuclear charge for a comparable…

Because Group 14 atoms are comparatively small for their nuclear charge, they are slightly more electronegative than the corresponding Group 13 elements.

All five Group 14 elements are solids at room temperature. Carbon and silicon behave as non-metals, germanium is a metalloid, and tin and lead are soft, low-melting metals.

Oxidation states. With four valence electrons, Group 14 elements mainly show +4 and +2 states (carbon additionally shows negative states in its many hydrides/organic compounds).

Just as boron stands apart from the rest of Group 13, carbon behaves quite differently from the rest of Group 14.

Carbon's ability to show allotropy comes directly from the two properties introduced in §11.5.6: its strong tendency to catenate (link into chains/rings via very strong C–C bonds) and its unique abili…

In diamond, every carbon atom is hybridised and covalently bonded to four neighbouring carbon atoms arranged tetrahedrally, with a C–C bond length of 154 pm (Fig.

Graphite has a layered structure built from planar hexagonal rings of carbon atoms (Fig. 11.4 shows the stacked hexagonal sheets).

Fullerenes are made by heating graphite in an electric arc under an inert atmosphere (helium or argon).

- Graphite fibres embedded in plastic give high-strength, lightweight composites used in tennis rackets, fishing rods, aircraft parts and canoes.

Carbon and silicon each form technologically important compounds built on their bonding preferences. For carbon, the two key oxides — carbon monoxide (CO) and carbon dioxide () — are taken up first.

Preparation. - Direct oxidation with limited oxygen/air: - Laboratory-scale: dehydrating formic acid () with concentrated at 373 K releases water and CO.

Preparation. Complete combustion of carbon and carbon-containing fuels in excess air gives : In the laboratory it is conveniently made by treating calcium carbonate with dilute HCl: Commercially it is…

About 95% of the earth's crust consists of silica and silicates. Silicon dioxide occurs in several interconvertible crystallographic forms — quartz, cristobalite and tridymite — which transform into o…

Silicones are organosilicon polymers built from a repeating unit, where R is an alkyl or aryl group. They are manufactured starting from alkyl- or aryl-substituted chlorosilanes, .

A large number of silicate minerals occur naturally, including feldspar, zeolites, mica and asbestos. The basic structural unit common to all silicates is the tetrahedral anion (Fig.

If aluminium atoms replace some of the silicon atoms within the three-dimensional network, the resulting framework is called an aluminosilicate.