Given below are two statements : One is labelled as Assertion A and the other is labelled as Reason R : Assertion (A) : {BeCl}_{2} and {MgCl}_{2} produce characteristic flame Reason (R) : The excitation energy is high in {BeCl}_{2} and {MgCl}_{2} the light of the above statements, choose the correct answer from the options given below :

Both (A) and (R) are true and (R) is the correct explanation of (A)

Both (A) and (R) are true but (R) is NOT the correct explanation of (A)

Better method for preparation of {BeF}_{2} , among the following is :

\left( {NH}_{4} \right)_{2}{BeF}_{4}\overset{\Delta}{\rightarrow}{BeF}_{2}

{BeH}_{2} + F_{2}\overset{\Delta}{\rightarrow}{BeF}_{2}

Be + F_{2}\overset{\Delta}{\rightarrow}{BeF}_{2}

BeO + C + F_{2}\overset{\Delta}{\rightarrow}{BeF}_{2}

JEE Main · Chemistry · Chapter 9

The s-Block Elements JEE Main PYQs (2020–2024)

89 questions from The s-Block Elements have appeared in JEE Main between 2020 and 2024, including 89 in the last five papers (2020–2024). The most-asked topic is Anomalous Properties of Li & Be and Diagonal Relationships (25 questions). Practise them all with instant answers and step-by-step solutions.

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Solved The s-Block Elements PYQs

3 recent questions with answers. The full set of 89 is free to practise.

JEE Main 2023MediumGroup 2: Alkaline Earth Metals - Trends & Physical Properties
Q1
Given below are two statements : One is labelled as Assertion A and the other is labelled as Reason R :

Assertion (A) : $B e Cl_{2}$ and $M g Cl_{2}$ produce characteristic flame

Reason (R) : The excitation energy is high in $B e Cl_{2}$ and $M g Cl_{2}$

the light of the above statements, choose the correct answer from the options given below :
- A $(A)$ is true but $(R)$ is false
- BBoth (A) and $(R)$ are true and $(R)$ is the correct explanation of $(A)$
- Cis false but (R) is true
- DBoth (A) and (R) are true but (R) is NOT the correct explanation of (A)
Show answer & solution
Correct answer: (C)
BeCl2 and MgCl2 do not produce characteristicbecause excitation energy is high in BeCl2MgCl2. Hence, the correct answer is option (C).
JEE Main 2023EasyAnomalous Properties of Li & Be and Diagonal Relationships
Q2
Better method for preparation of $B e F_{2}$ , among the following is :
- A $B eH_{2} + F_{2} \to Δ B e F_{2}$
- B $(N H_{4})_{2} B e F_{4} \to Δ B e F_{2}$
- C $B e + F_{2} \to Δ B e F_{2}$
- D $B e O + C + F_{2} \to Δ B e F_{2}$
Show answer & solution
Correct answer: (B)
According to the NCERT (s block) textbook, the better method for the preparation of BeF₂ is heating (NH₄)₂BeF₄.

B :

$(N H_{4})_{2} B e F_{4} \to Δ B e F_{2} + 2 N H_{4} F$

method involves the thermal decomposition of ammonium beryllium fluoride ((NH₄)₂BeF₄) to form beryllium fluoride (BeF₂) and ammonium fluoride (NH₄F). The reaction is more efficient compared to other options and results in a purer product.
JEE Main 2023MediumGroup 1: Alkali Metals - Trends & Physical Properties
Q3
Identify the correct order of standard enthalpy of formation of sodium halides :
- A $N a I < N a B r < N a Cl < N a F$
- B $N a I < N a B r < N a F < N a Cl$
- C $N a F < N a Cl < N a B r < N a I$
- D $N a Cl < N a F < N a B r < N a I$
Show answer & solution
Correct answer: (A)
Lattice energy is directly proportional to the charges of the ions and inversely proportional to the sum of their radii:

energy ∝ (Q₁Q₂) / (r₁ + r₂)

As we move down the group, the size of the halide ions increases, resulting in a decrease in lattice energy. This leads to a decrease in the exothermicity of the lattice energy release during the formation of sodium halides.

Thus, the correct order of standard enthalpy of formation of sodium halides, considering both lattice energy and electron affinity, is:

$N a F > N a Cl > N a B r > N a I$

Practise all 89 The s-Block Elements PYQs

Topic-wise question count

Where JEE Main has asked from The s-Block Elements, most frequent first.

Anomalous Properties of Li & Be and Diagonal Relationships25
Group 1: Alkali Metals - Trends & Physical Properties15
Group 2: Important Compounds (CaO, CaCO3, Ca(OH)2, Plaster of Paris)13
Group 2: Alkaline Earth Metals - Trends & Physical Properties10
Group 1: Chemical Reactivity & Flame Coloration9
Group 1: Important Compounds (Na2CO3, NaOH, NaCl, NaHCO3)8
Group 2: Chemical Reactivity & Trends in Compounds5
Biological Importance of Na, K, Mg, Ca4

Year-wise The s-Block Elements questions in JEE Main

Number of questions from this chapter in each year's paper(s).

2024

2023

2022

2021

2020

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