Ch 11 covers Groups 13 (boron family) and 14 (carbon family) of the p-block. Students learn about trends, important compounds, allotropy, and the inert pair effect.
Configuration: ns²np¹. Boron: metalloid, others are metals. BF₃ is electron-deficient (Lewis acid, accepts lone pair into empty p-orbital). Borax (Na₂B₄O₇·10H₂O): borax bead test for metallic radicals. Boric acid B(OH)₃: weak monobasic Lewis acid. Aluminium: amphoteric (reacts with both acids and bases). Al₂O₃: corundum (very hard).
Configuration: ns²np². Carbon: catenation (ability to form long chains), allotropes (diamond — sp³, hardest; graphite — sp², conductor, layers; fullerene — C₆₀; graphene). Metallic character increases down the group (C,Si non-metals; Ge metalloid; Sn,Pb metals). Inert pair effect: Sn prefers Sn²⁺, Pb prefers Pb²⁺. Important: SiO₂ (quartz), CO₂ vs SiO₂ (molecular vs network solid).
Download: https://ncert.nic.in/textbook/pdf/kech204.pdf | Part II: https://ncert.nic.in/textbook/pdf/kech2ps.zip
In heavier p-block elements (Groups 13-15), the two ns² electrons (s-pair) resist participating in bonding. This is because poor shielding by d and f electrons increases the effective nuclear charge on s-electrons, holding them tighter. So Pb prefers +2 (not +4), Tl prefers +1 (not +3). This trend increases down a group.
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