The s block Elements 11TH CHEM E

Описание: The s block Elements 11TH CHEM E
In Class 11 Chemistry, the s-block consists of
Group 1 and Group 2 elements. These are atoms where the last electron enters the outermost s-orbital. 

Important points
Group 1 element: alkali metals, 

General characteristics of the compounds of the alkali metals, 

Anomalous properties of Lithium, 

Some important compounds of sodium, 

Biological importance of sodium and potassium, 

Group 2 elements: alkaline earth metals, 

General characteristics of compounds of the alkaline earth metals, 

Anomalous behaviour of beryllium, 

Some important compounds of calcium,   

Biological importance of magnesium and calcium.






1. Group 1: Alkali Metals 

Elements: Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Caesium (Cs), and Francium (Fr
.
Key Traits: 
Very soft, low melting points, and highly reactive (usually stored in kerosene).
Flame Colour: They give distinct colours (e.g., Li is crimson, Na is yellow) because their outermost electron is easily excited. 

2. Group 2: Alkaline Earth Metals 

Elements: Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), and Radium (Ra).

Key Traits: 
Harder and denser than Group 1, with higher melting points.

Reactivity: Less reactive than alkali metals but still form basic oxides and hydroxides. 

Important Concepts for Exams

Anomalous Properties: Lithium and Beryllium behave differently from their groups due to their exceptionally small size and high charge density.

Diagonal Relationship:
 Li resembles Mg, and Be resembles Al in many chemical properties.

Biological Importance: 
Sodium and Potassium are vital for nerve signals, while Magnesium and Calcium are essential for bones and enzyme functions.

Compounds to Know: 
Sodium Carbonate (Washing Soda), Sodium Chloride, Sodium Hydroxide (Caustic Soda), and Calcium Oxide (Quicklime). 

s-block is defined by its two groups: Group 1 (Alkali Metals) and
 Group 2 (Alkaline Earth Metals). Here is a breakdown of their chemistry and the unique trends you'll need for exams.

1. Physical Trends (Group 1 vs. Group 2)

Atomic Radii: Atoms get larger as you go down the group (more shells). Group 1 atoms are generally larger than Group 2 atoms in the same period because they have a lower nuclear charge.

Ionization Enthalpy: This decreases down the group. Group 1 has very low 1st I.E., making them extremely reactive. Group 2 has higher I.E. than Group 1 but still relatively low.

Hydration Enthalpy: Smaller ions attract water molecules more stron

Result: Lithium salts are usually hydrated (e.g., 

2. Chemical Properties

Reactivity with Air:

Group 1: Form oxides 

 peroxides 

or superoxides 


Group 2: Form oxides

and nitrides
Beryllium and Magnesium are relatively inert due to an oxide film.

Reactivity with Water: They release hydrogen gas and form hydroxides. Group 1 reacts explosively; Group 2 is calmer (Mg needs hot water).
Solutions in Liquid Ammonia: Both groups dissolve in liquid ammonia to give deep blue solutions. These are conducting and paramagnetic because of ammoniated electrons.

3. Anomalous Behavior & Diagonal Relationship

The first element of each group (Li and Be) behaves differently because they are tiny and have high polarizing power.

Diagonal Relationship: Lithium behaves like Magnesium, and Beryllium behaves like Aluminium.

Why? They have similar ionic sizes and charge-to-radius ratios.

 are deliquescent (absorb moisture) and soluble in ethanol.

4. Important Industrial Compounds

Sodium Carbonate

): Known as Washing Soda, prepared by the Solvay Process.

Sodium Hydroxide

 Known as Caustic Soda, prepared in the Castner-Kellner cell.

Calcium Oxide (

): Known as Quicklime. Adding water to it is called "slaking of lime," which produces Slaked Lime 
Plaster of Paris
 Formed by heating Gypsum

to 393 K.

5. Biological Role

 Pump: Essential for maintaining cell membrane potential and nerve impulse transmission.


: Required for all enzymes using ATP in phosphate transfer and is the central atom in chlorophyll

: Crucial for blood clotting, bone structure, and muscle contraction.