s-Block Elements: Visual Guide (Tables + Reactions + Trends)

Periodic Position of s-Block

Period 2:  Li  Be
Period 3:  Na  Mg
Period 4:  K   Ca
Period 5:  Rb  Sr
Period 6:  Cs  Ba
           ↑    ↑
         Group 1  Group 2

Oxide Type Trend Down Group 1

Metal	Cation Size	Oxide Formed	Anion
Li	Smallest ↓	$Li_{2}O$ (normal)	$O^{2-}$ (oxide)
Na	Small	$Na_{2}O_{2}$ (peroxide)	$O_{2}^{2-}$ (peroxide)
K	Medium	$KO_{2}$ (superoxide)	$O_{2}^{-}$ (superoxide)
Rb	Large	$RbO_{2}$ (superoxide)	$O_{2}^{-}$
Cs	Largest ↑	$CsO_{2}$ (superoxide)	$O_{2}^{-}$

Trend: as cation size ↑, the stabilized anion size ↑ (lattice energy effect).

Solvay Process — Step-by-Step Flow

NaCl(aq) + $NH_{3}$(g)
        ↓ + $CO_{2}$(g) + $H_{2}O$
   $NaHCO_{3}$↓ (precipitates — least soluble)
        ↓ heat
     $Na_{2}CO_{3}$ + $CO_{2}$ + $H_{2}O$

$NH_{4}Cl$(aq) + Ca(OH)_{2} → $NH_{3}$↑ (recycled) + $CaCl_{2}$ + $H_{2}O$

Diagonal Relationships — Visual Comparison

Li  →  Na  →  K  ...      (Group 1, Period 2, 3, 4)
↘
Mg  →  Ca  ...             (Group 2, Period 3, 4)

Be  →  Mg  →  Ca ...      (Group 2, Period 2, 3, 4)
↘
Al  →  Si  ...             (Group 13, Period 3)

Calcium Compound Interconversion

$CaCO_{3}$ --[1073 K, $\Delta$]--> CaO + $CO_{2}$ CaO + $H_{2}O$ --[exothermic]--> Ca(OH)_{2} Ca(OH)_{2} + $CO_{2}$ --[air]--> $CaCO_{3}$ + $H_{2}O$ (whitewashing — reversible cycle) $CaSO_{4}$·2$H_{2}O$ --[373 K]--> $CaSO_{4}$·½$H_{2}O$ + 3/2$H_{2}O$ (gypsum → Plaster of Paris) $CaSO_{4}$·½$H_{2}O$ + 3/2$H_{2}O$ --[setting]--> $CaSO_{4}$·2$H_{2}O$ (exothermic, slight expansion)

Flame Color Test — Visual Reference

Metal	Wavelength (nm)	Color
Li	~671	Crimson red
Na	~589 (D-line)	Golden yellow
K	~766	Violet
Rb	~780	Red-violet
Cs	~455	Blue

Na gives the brightest and most distinctive flame — easiest to identify in the lab.

Ionization Enthalpy Trend (Group 1)

$IE_1: \text{Li}(520) > \text{Na}(496) > \text{K}(419) > \text{Rb}(403) > \text{Cs}(376) \text{ kJ/mol} \downarrow$

The decrease is due to increasing atomic radius and greater shielding by inner electrons — the outermost $ns^{1}$ electron is progressively further from the nucleus and more shielded.