RBSE Class 11 Chemistry Notes Chapter 10 The s-Block Elements

These comprehensive RBSE Class 11 Chemistry Notes Chapter 10 The s-Block Elements will give a brief overview of all the concepts.

RBSE Class 11 Chemistry Chapter 10 Notes The s-Block Elements

→ Alkali Metals: First group of s-block elements is known as alkali metals because their oxides gives strong base on mixing with water.

→ Physical Properties of Alkali Metals:

• Li < Na Li⁺ < Na⁺ < K⁺ + <Fr⁺ (Ionic radius)
• Li > Na > K > Rb> Cs > Fr (Ionisation energy)
• Li < Na < K < Rh < Cs < Fr (Electropositive character) Li> Na > K > Rb > Cs > Fr (Electronegativity)
• Li > Na > K > Rb > Cs > Fr (Boiling and Melting Points)
• Na < K < Rb < Cs < Li (Reducing properties)
• Li⁺ > Na⁺ > K⁺ > Rb⁺ > Cs⁺ (Hydration energy)

→ Polarisation: Distortion of electron cloud of anion due to cation is called polarisation.

→ Fajan’s Rule: According to the rule, polarization will be increased by:

• High charge and small size of the cation.
• High charge and large size of the anion.
• The polarizability of an anion is related to the deformability of its electron cloud (i.e., its “softness”).
• An incomplete valence shell electron configuration. Noble gas configuration of the cation produces better shielding and less polarizing power.

→ Soda Ash: Anhydrous sodium carbonate is called soda ash because it is found in ash of some aquatic plants.

→ Washing Soda: Sodium carbonate is called washing soda because it is used in washing clothes.

→ Baking Soda: Sodium bicarbonate is called baking soda. 

→ Caustic Soda: Sodium hydroxide is called caustic soda:

→ Alkaline Earth Metals: Group 2 of s-block elements is known as alkaline earth metals because their hydroxides are strong alkali (just like those of alkali metals) and these all are found in earth crust.

→ Milk of Magnesia: When magnesium is heated with boiled water or steam, it forms magnesium hydroxide. This is known as “Milk of Magnesia”.

→ Properties of Alkaline Earth Metals

• Be < Mg < Ca < Sr < Ba < Ra (Atomic radius)
• Be²⁺ < Mg²⁺ < Ca²⁺ < Sr²⁺ < Ba²⁺ (Ionic radius)
• Be < Mg
• Be²⁺ < Mg²⁺ < Ca²⁺ < Sr²⁺ < Ba²⁺ (Hydration energy)

→ Magnelium: It is an alloy which has 95% Al, and 5% Mg. It is used in making aircraft parts, making piston of engines etc. 

→ Electron Metal: It is an alloy which has 95% Mg, and 5% Zn. It is used in making aircraft parts.

→ Duralumin: It is an alloy which has 95% Al, 0.5% Mg, and 4% Cu. lt is used for making parts of ship.

→ General Characteristics off Compounds off Alkaline Earth Metals

• BeO < MgO < CaO < SrO < BaO (Alkaline strength)
• Be(OH)₂ < Mg(OH)₂ < Ca(OH)₂ < Sr(OH)₂ < Ba(OH)₂ (Alkaline strength)
• BeCO₃> MgCO₃ > CaCO₃ > SrCO₃ >BaCO₃ (Solubility)
• BeCO₃ < MgCO₃ < CaCO₃ < SrCO₃ < BaCO₃ (Thermal Stability)
• BeSO₄ < MgSO₄ < CaSO₄ < SrSO₄ < BaSO₄ (Thermal Stability)
• BeSO₄ > MgSO₄ > CaSO₄ > SrSO₄ > BaSO₄ (Solubility)
• Be(NO₃)₂ < Mg(NO₃)₂ < Ca(NO₃)₂ < Sr(NO₃)₂ < Ba(NO₃)₂ (Solubility)
• Be(NO₃)₂ < Mg(NO₃)₂ <Ca(NO₃)₂ < Sr(NO₃)₂ < Ba(NO₃)₂ (Thermal Stability)

→ Lime Water: Quick lime is a solid. It is mixed with water and called as lime water.

→ Important Points:

• Na and K are stored in kerosene oil because it reacts with atmospheric vapour and form oxides.
• Li is kept wrapped in paraffin wax because it floats on kerosene because of low density.
• Among alkali metals carbonates, only lithium carbonate decomposes and gives carbon dioxide.
• All alkali metals are strong reducing agents but lithium is strongest reducing agent among all.
• Fire caught by alkali metals cannot be extinguished by water but can be extinguished by spraying CCl₄.
• All alkali metals and alkaline earth metals except Be and Mg gives flame test. .
• The order of solubility of sulphates of alkaline earth metals in water is:
  BeSO₄ > MgSO₄ > CaSO₄ > SrSO₄ > BaSO₄
• The order of solubility of carbonates of alkaline earth metals in water is:
  BeCO₃ > MgCO₃ > CaCO3 > SrCO₃ > BaCO₃
• Alkali metals dissolve in liquid ammonia and give blue conducting solution.
• Lithium forms monoxide, sodium forms peroxide and others form superoxides.
• Sodium carbonate is prepared by Solvay Method.