Ch 10 covers the s-block elements — alkali metals (Group 1) and alkaline earth metals (Group 2) — their electronic configuration, properties, compounds, and the diagonal relationship.
Configuration: ns¹. Soft, low melting point, highly reactive. Reactivity increases down group. React vigorously with water (2Na + 2H₂O → 2NaOH + H₂↑). Flame colours: Li-crimson, Na-golden yellow, K-violet. Important compounds: NaOH (caustic soda), Na₂CO₃ (washing soda, Solvay process), NaHCO₃ (baking soda), KOH.
Configuration: ns². Harder than Group 1, higher mp. Mg/Ca important biologically. CaO (quicklime) + H₂O → Ca(OH)₂ (slaked lime). CaSO₄·½H₂O: plaster of Paris. CaCO₃: limestone. Diagonal relationship: Li behaves like Mg; Be behaves like Al — due to similar charge/radius ratio (polarising power).
Download: https://ncert.nic.in/textbook/pdf/kech203.pdf | Part II: https://ncert.nic.in/textbook/pdf/kech2ps.zip
Down Group 1, atomic size increases → ionisation energy decreases → it becomes easier to lose the outermost electron. Sodium (larger atom, lower IE) loses its valence electron more readily than lithium, making it more reactive with water. The trend continues: K reacts even more vigorously than Na.
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