Exam Master Review Sheet - s-Block Elements

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EXAM MASTER REVIEW SHEET

s-Block Elements (Groups 1 & 2)

Strategic Summary for JEE Main, Advanced & NEET

1. Group 1: Alkali Metals (\(ns^1\))

Hydration Enthalpy

\(Li^+ > Na^+ > K^+ > Rb^+ > Cs^+\)

*Smaller ion, higher hydration, lower ionic mobility.*

Flame Coloration

Li: Crimson | Na: Golden Yellow | K: Violet | Rb: Red-Violet | Cs: Blue

Solution in Liquid Ammonia

\[ M + (x+y)NH_3 \longrightarrow [M(NH_3)_x]^+ + [e(NH_3)_y]^- \]

Deep Blue Color due to Ammoniated Electrons.

*Paramagnetic and powerful reducing agent.*

2. Group 2: Alkaline Earth Metals (\(ns^2\))

Property	Trend Down the Group	Comparison with Gr 1
Atomic Size	Increases	Smaller than Gr 1
Ionization Enthalpy	Decreases	Higher than Gr 1
Hardness/M.P.	Irregular	Harder; Higher M.P.

Flame Test Note: Be and Mg do not give flame color due to high ionization energy (electrons not excited by Bunsen flame).

3. Diagonal Relationships

Lithium & Magnesium

• Both form Nitride: \(Li_3N\) and \(Mg_3N_2\).
• Carbonates decompose on heating to form oxides.
• Chlorides (\(LiCl, MgCl_2\)) are deliquescent and soluble in ethanol.

Beryllium & Aluminium

• Both are rendered passive by \(HNO_3\) (oxide film).
• Both form Amphoteric oxides and hydroxides.
• Chlorides (\(BeCl_2, AlCl_3\)) form bridged polymeric structures in vapor.

4. Industrial Compounds

Solvay Process (\(Na_2CO_3\))

\(NH_3 + H_2O + CO_2 \to NH_4HCO_3\)
\(NH_4HCO_3 + NaCl \to NaHCO_3 \downarrow + NH_4Cl\)
\(2NaHCO_3 \xrightarrow{\Delta} Na_2CO_3 + H_2O + CO_2\)

Plaster of Paris (\(CaSO_4 \cdot \frac{1}{2}H_2O\))

Obtained by heating Gypsum (\(CaSO_4 \cdot 2H_2O\)) at 393 K.
Above 473 K: Dead burnt plaster (\(CaSO_4\)) forms.

Castner-Kellner Cell: Electrolysis of Brine for production of \(NaOH\). Mercury cathode is used to form Na-amalgam.

5. Solubility & Stability Trends

Thermal Stability

Stability of Carbonates / Sulfates:

Increases down the group

Due to decrease in polarizing power of the cation.

Solubility in Water

Group 2 Hydroxides:

Increases (\(Be \to Ba\))

Group 2 Sulfates:

Decreases (\(Be \to Ba\))

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