2.1 General Characteristics of s-Block Elements

Both groups have low ionization enthalpies, large atomic radii, and high reactivity. Down each group, atomic radius increases, IE decreases, and metallic character increases. Group 1 elements always form +1 ions; Group 2 always form +2 ions. s-Block elements are strong reducing agents and react vigorously with air and water.

2.2 Group 1 — Physical and Chemical Properties

All alkali metals dissolve in liquid $NH_{3}$ to form blue (dilute) or bronze (concentrated) solutions containing solvated electrons, which are strong reducing agents.

2.3 Anomalous Behavior of Lithium

Li is anomalous because its ionic radius (76 pm) is disproportionately small, giving it the highest charge density in the group. This causes covalent character in its compounds (LiCl soluble in ethanol), high hydration enthalpy ($Li^{+}$ is the most heavily hydrated ion despite being the smallest), and properties mirroring magnesium (diagonal relationship).

2.4 Important Reactions and Compound Chemistry — Group 1

• NaOH: 2NaCl + 2$H_{2}O$ →(electrolysis) 2NaOH + $Cl_{2}$↑ + $H_{2}$↑ (chlor-alkali / Castner-Kellner)
• $Na_{2}CO_{3}$: Solvay process — involves NaCl, $NH_{3}$, $CO_{2}$, water. $NaHCO_{3}$ precipitates first (least soluble), then heated to $Na_{2}CO_{3}$
• $NaHCO_{3}$ decomposition: 2$NaHCO_{3}$ →($\Delta$) $Na_{2}CO_{3}$ + $CO_{2}$ + $H_{2}O$
• Bleaching powder: Ca(OH)_{2} + $Cl_{2}$ → CaO$Cl_{2}$ + $H_{2}O$

2.5 Anomalous Behavior of Beryllium

Be is anomalous because it has the smallest atomic radius, no d-orbitals, and maximum covalency of 4. It forms the only amphoteric oxide in Group 2. Be$Cl_{2}$ has a linear geometry but forms a polymeric chain in solid state with chlorine bridges (Cl-bridged structure). The diagonal relationship with Al is heavily tested.

2.6 Calcium Compounds — Industrial Significance

• Mortar: Ca(OH){2} + sand; sets by carbonation ($CO_{2}$ from air converts Ca(OH){2} → $CaCO_{3}$)
• Cement setting: Hydration of silicates and aluminates; gypsum retards this reaction
• Plaster of Paris: Used in surgical casts; sets exothermically with slight expansion (important for fitting)

2.7 Biological Roles of s-Block Ions

The body maintains strict concentration gradients: [$Na^{+}$] is high extracellularly, [$K^{+}$] high intracellularly. This gradient is maintained by the $Na^{+}$-$K^{+}$ ATPase pump (3 $Na^{+}$ out, 2 $K^{+}$ in per cycle using ATP). Disruption causes cardiac arrhythmias and neurological disorders.