How much of JEE Main comes from Hydrogen s-Block and p-Block Elements?

JEEGenie estimates about 6% of JEE Main marks come from Hydrogen s-Block and p-Block Elements, based on recent papers. The share varies from year to year.

Which formulas matter most in Hydrogen s-Block and p-Block Elements?

The Hydrogen s-Block and p-Block Elements sheet on this page has 13 formula entries, starting with Water Gas Shift Reaction, Hardness of Water Removal, Reaction of Alkali Metals with Water, Thermal Decomposition of Carbonates, Preparation of Borax (Na₂B₄O₇·10H₂O). Each one comes with when to use it and the trap to avoid.

What topics does Hydrogen s-Block and p-Block Elements cover for JEE?

Hydrogen s-Block and p-Block Elements covers Hydrogen and Hydrides, Alkali Metals, Alkaline Earth Metals, Group 13-14 Elements, Group 15-18 Elements, Diagonal Relationship.

How should I revise Hydrogen s-Block and p-Block Elements before the exam?

Learn each formula together with its condition of use, read the trap listed beside it, then practise questions and review every mistake. The practice link on this page opens Hydrogen s-Block and p-Block Elements questions on JEEGenie.

How many previous-year questions are there on Hydrogen s-Block and p-Block Elements?

JEEGenie has 1065 previous-year questions on Hydrogen s-Block and p-Block Elements, and this page shows a few with worked explanations.

Is practice on Hydrogen s-Block and p-Block Elements free on JEEGenie?

Sign-up is free and includes a 7-day Pro trial. After the trial, free accounts keep a limited daily quota.

Hydrogen s-Block and p-Block Elements for JEE Main & Advanced — formulas, what is asked, and traps

JEEGenie estimates about 6% of JEE Main marks come from Hydrogen s-Block and p-Block Elements. This page covers 13 formula entries, each with when to use it, what JEE asks and the traps. A common slip: Do not assume hydrogen is a metal; it is a non-metal under standard conditions.

Key points to know

Position of Hydrogen. Hydrogen resembles both alkali metals (group 1) and halogens (group 17) due to its unique electronic configuration (1s¹), but it is placed separately in the periodic table.
Isotopes of Hydrogen. Hydrogen has three isotopes: protium (¹H), deuterium (²H or D), and tritium (³H or T), with tritium being radioactive.
Alkali Metals (Group 1) General Trends. Alkali metals (Li, Na, K, Rb, Cs, Fr) are highly reactive, soft, with low melting points; reactivity increases down the group due to decreasing ionization enthalpy.
Anomalous Behavior of Lithium. Lithium differs from other alkali metals due to its small size, high polarizing power, and strong covalent character in its compounds.
Alkaline Earth Metals (Group 2) General Trends. Alkaline earth metals (Be, Mg, Ca, Sr, Ba, Ra) are less reactive than alkali metals, with higher melting points and ionization enthalpies; reactivity increases down the group.
Diagonal Relationship: Li and Mg. Lithium and magnesium show similarities due to similar size and charge density: both form nitrides, carbonates decompose on heating, and hydroxides are weak bases.
Allotropes of Carbon. Carbon has several allotropes: diamond (sp³, hard, insulator), graphite (sp², soft, conductor), fullerenes (C₆₀, soccer-ball shape), and graphene (single layer of graphite).
Silicones. Silicones are organosilicon polymers with Si-O backbone and organic groups (R₂SiO), known for water repellency, thermal stability, and electrical insulation.
Oxides of Nitrogen. Nitrogen forms several oxides: N₂O (laughing gas, linear), NO (radical), N₂O₃ (blue liquid), NO₂ (brown gas, paramagnetic), N₂O₄ (dimer), N₂O₅ (white solid).
Phosphorus Allotropes. Phosphorus exists as white (P₄, tetrahedral, highly reactive), red (polymeric, less reactive), and black (most stable, layered) allotropes.
Sulfur Allotropes. Sulfur has many allotropes: rhombic (α-sulfur, stable below 96°C), monoclinic (β-sulfur, stable above 96°C), and plastic (amorphous, unstable).
Sulfuric Acid: Contact Process. Sulfuric acid is manufactured by the Contact Process: burning S to SO₂, catalytic oxidation to SO₃ (V₂O₅ catalyst), and absorption in H₂SO₄ to form oleum.

Formula sheet

Name	Formula	When to use
Water Gas Shift Reaction	$CO + H_{2} O \overset{catalyst}{\to} {CO}_{2} + H_{2}$	When solving problems on industrial hydrogen production or thermochemical cycles.
Hardness of Water Removal	${Ca(HCO}_{3})_{2} \overset{Δ}{\to} {CaCO}_{3} ↓ + H_{2} O + {CO}_{2}$	When solving water treatment problems or distinguishing between hardness types.
Reaction of Alkali Metals with Water	$2 M + 2 H_{2} O \to 2 MOH + H_{2} ↑$	When writing equations for alkali metal reactions or predicting products.
Thermal Decomposition of Carbonates	${MCO}_{3} \overset{Δ}{\to} MO + {CO}_{2} ↑$	When predicting products of heating metal carbonates or comparing thermal stability.
Preparation of Borax (Na₂B₄O₇·10H₂O)	${Ca}_{2} B_{6} O_{11} + 2 {Na}_{2} {CO}_{3} \to {Na}_{2} B_{4} O_{7} + 2 {CaCO}_{3} ↓ + 2 {NaBO}_{2}$	When writing industrial preparation of boron compounds or in qualitative analysis.
Silicones	$R_{2} {SiCl}_{2} + H_{2} O \to R_{2} {Si(OH)}_{2} \overset{polymerization}{\to} (R_{2} SiO)_{n}$	When discussing polymer chemistry or applications of silicon compounds.
Reaction of Silicon with Alkali	$Si + 2 NaOH + H_{2} O \to {Na}_{2} {SiO}_{3} + 2 H_{2} ↑$	When writing reactions of silicon or comparing with carbon (which does not react with alkali).
Borax Bead Test	${Na}_{2} B_{4} O_{7} \overset{Δ}{\to} 2 {NaBO}_{2} + B_{2} O_{3}$	When identifying metal ions in qualitative analysis.
Reaction of Ammonia with Chlorine	$8 {NH}_{3} + 3 {Cl}_{2} \to 6 {NH}_{4} Cl + N_{2}$ (excess NH₃; the HCl formed is taken up as NH₄Cl) ${NH}_{3} + 3 {Cl}_{2} \to {NCl}_{3} + 3 HCl$ (excess Cl₂)	When predicting products of ammonia reactions or in industrial chemistry.
Ostwald's Process for HNO₃	$4 {NH}_{3} + 5 O_{2} \overset{Pt/Rh}{\to} 4 NO + 6 H_{2} O$ $2 NO + O_{2} \to 2 {NO}_{2}$ $3 {NO}_{2} + H_{2} O \to 2 {HNO}_{3} + NO$	When solving industrial chemistry problems or writing the process steps.
Sulfuric Acid: Contact Process	$S + O_{2} \to {SO}_{2}$ $2 {SO}_{2} + O_{2} \overset{V_{2} O_{5}}{\to} 2 {SO}_{3}$ ${SO}_{3} + H_{2} {SO}_{4} \to H_{2} S_{2} O_{7}$ (oleum) $H_{2} S_{2} O_{7} + H_{2} O \to 2 H_{2} {SO}_{4}$
Reaction of Halogens with Water	$X_{2} + H_{2} O \to HX + HOX$ (for Cl₂, Br₂) $2 F_{2} + 2 H_{2} O \to 4 HF + O_{2}$	When writing reactions of halogens or comparing their oxidizing power.
Interhalogen Compounds	${Cl}_{2} + 3 F_{2} \to 2 {ClF}_{3}$	When predicting structures or reactions of halogen compounds.

Open the Hydrogen s-Block and p-Block Elements formula page

What JEE asks

Position of Hydrogen. JEE often asks why hydrogen is placed separately, or to compare its properties with alkali metals and halogens.
Isotopes of Hydrogen. JEE may ask about the number of neutrons or the use of deuterium in nuclear reactors.
Water Gas Shift Reaction. JEE may ask the balanced equation or the role of catalyst in this reaction.
Hardness of Water Removal. JEE often tests the chemical equations for removal methods or asks to identify the correct reagent.
Alkali Metals (Group 1) General Trends. JEE may ask about anomalous behavior of lithium or trends in ionization enthalpy.
Anomalous Behavior of Lithium. JEE often asks for specific reactions of lithium (e.g., with N₂, O₂) or its diagonal relationship with magnesium.
Reaction of Alkali Metals with Water. JEE may ask the color of flame or the relative reactivity order.
Flame Test for Alkali Metals. JEE may ask the flame color of a given metal or the reason for using cobalt glass.
Alkaline Earth Metals (Group 2) General Trends. JEE often tests the anomalous behavior of beryllium or trends in solubility.
Diagonal Relationship: Li and Mg. JEE may ask for specific reactions (e.g., formation of nitride) or properties.
Thermal Decomposition of Carbonates. JEE may ask the order of thermal stability or the decomposition temperature.
Preparation of Borax (Na₂B₄O₇·10H₂O). JEE may ask the balanced equation or the use of borax bead test.
Allotropes of Carbon. JEE often asks the hybridization or properties of each allotrope.
Silicones. JEE may ask the structure or uses of silicones (e.g., lubricants, sealants).
Reaction of Silicon with Alkali. JEE may ask the balanced equation or the product formed.
Borax Bead Test. JEE may ask the color for a given metal or the chemistry behind the test.
Oxides of Nitrogen. JEE often asks the structure, hybridization, or magnetic behavior of these oxides.
Phosphorus Allotropes. JEE may ask the structure of P₄ or the stability order.
Reaction of Ammonia with Chlorine. JEE may ask the conditions for each product or the balanced equation.
Ostwald's Process for HNO₃. JEE may ask the catalyst, temperature, or balanced equations.
Sulfur Allotropes. JEE may ask the transition temperature or the structure of S₈ rings.
Sulfuric Acid: Contact Process. JEE may ask the catalyst, the reason for using oleum, or the balanced equations.
Reaction of Halogens with Water. JEE may ask the product for a specific halogen or the trend in reactivity.
Interhalogen Compounds. JEE may ask the geometry or hybridization of interhalogens like ClF₃ or IF₇.

Common traps

Do not assume hydrogen is a metal; it is a non-metal under standard conditions. Position of Hydrogen
Tritium is radioactive with a half-life of 12.3 years, not stable. Isotopes of Hydrogen
The catalyst is usually iron oxide or chromium oxide, not just any metal. Water Gas Shift Reaction
Boiling only removes temporary hardness, not permanent. Hardness of Water Removal
Lithium is the least reactive, not sodium; it forms a nitride (Li₃N) unlike others. Alkali Metals (Group 1) General Trends
Lithium forms a nitride (Li₃N) with N₂, but other alkali metals do not. Anomalous Behavior of Lithium
Lithium does not produce a flame; sodium produces a yellow flame; potassium produces a lilac flame. Reaction of Alkali Metals with Water
Sodium's yellow flame is so intense it can mask other colors; use cobalt glass to filter it. Flame Test for Alkali Metals
Beryllium is amphoteric, not basic like other group 2 elements. Alkaline Earth Metals (Group 2) General Trends
This relationship is between Li (group 1) and Mg (group 2), not Li and Be. Diagonal Relationship: Li and Mg
BeCO₃ is unstable and decomposes at ~100°C, while BaCO₃ requires >1000°C. Thermal Decomposition of Carbonates
The product is not pure borax; sodium metaborate (NaBO₂) is a byproduct. Preparation of Borax (Na₂B₄O₇·10H₂O)
Diamond is the hardest natural substance, but graphite is soft and slippery. Allotropes of Carbon
Silicones are not based on carbon; they have Si-O bonds, not C-C. Silicones

Topics in Hydrogen s-Block and p-Block Elements

Hydrogen and Hydrides
Alkali Metals
Alkaline Earth Metals
Group 13-14 Elements
Group 15-18 Elements
Diagonal Relationship

Previous-year questions on Hydrogen s-Block and p-Block Elements

JEEGenie has 1065 previous-year questions on Hydrogen s-Block and p-Block Elements. A few worked examples follow.

Year	Questions
2026	26
2025	27
2024	44
2023	134
2022	130
2021	138
2020	52
2019	114
2018	24
2017	21
2016	36
2015	19
2014	20
2013	14
2012	15
2011	9
2010	6
2009	7
2008	9
2007	15
2006	8
2005	13
2004	16
2003	13
2002	20
2001	8
2000	5
1999	6
1998	14
1997	7
1996	11
1995	1
1994	7
1993	7
1992	7
1991	6
1990	4
1989	4
1988	3
1987	7
1986	6
1985	6
1984	2
1983	6
1982	3
1981	5
1980	6
1979	1
1978	3

Question 1 medium

The electronegativity of a group 13 element ' E ' is same as that of Ge (on Pauling scale and upto one decimal point). The CORRECT statements about

E^{3 +}

are A. It can act as a reducing agent. B. It can act as an oxidizing agent. C.

E^{3 +}

is more stable than

E^{+}

. D. The standard electrode potential value for

E^{3 +} / E

is positive. Choose the correct answer from the options given below :

A and C Only
B and C Only
B and D Only
A and D Only

Answer: C

Explanation. The element

E

is Thallium (Tl), as its Pauling electronegativity is

1.8

, matching that of Ge. For

{T l}^{3 +}

: 1. **Oxidizing agent**:

{T l}^{3 +}

readily gains electrons to form the more stable

{T l}^{+}

(inert pair effect). Hence, it acts as an oxidizing agent. Statement B is correct. 2. **Stability**: Due to the inert pair effect,

{T l}^{+}

is more stable than

{T l}^{3 +}

. Statement C is incorrect. 3. **Reducing agent**: Since

{T l}^{3 +}

tends to be reduced, it does not act as a reducing agent. Statement A is incorrect. 4. **Standard electrode potential**:

{T l}^{3 +} + 3 e^{-} \to T l

has

E^{\circ} = + 0.72 V

, which is positive. Statement D is correct. Thus, the correct statements are B and D.

C

From NTA/IIT papers: JEE Main 2026 · 4 Apr Shift 2

Question 2 easy

Formation of

{N a}_{4} [F e (C N)_{5} N O S]

, a purple coloured complex formed by addition of sodium nitroprusside in sodium carbonate extract of salt indicates the presence of :

Sulphide ion
Sulphite ion
Sulphate ion
Sodium ion

Answer: A

Explanation. The purple complex

{N a}_{4} [F e (C N)_{5} N O S]

forms when sodium nitroprusside reacts with sulphide ions in alkaline medium. Step 1: Sodium nitroprusside is

{N a}_{2} [F e (C N)_{5} N O]

. Step 2: In the presence of

S^{2 -}

ions (from sodium carbonate extract), the nitroprusside ion reacts:

{[F e (C N)_{5} N O]}^{2 -} + S^{2 -} \to {[F e (C N)_{5} N O S]}^{4 -}

Step 3: This yields a purple colour, confirming the presence of sulphide ion. Thus, the answer is option A.

From NTA/IIT papers: JEE Main 2025 · 2 Apr Shift 2

Question 3 hard

At room temperature, disproportionation of an aqueous solution of in situ generated nitrous acid (HNO

_{2}

) gives the species

H $_{3}$ O $^{+}$ , NO $_{3}^{-}$ and NO
H $_{3}$ O $^{+}$ , NO $_{3}^{-}$ and NO $_{2}$
H $_{3}$ O $^{+}$ , NO $^{-}$ and NO $_{2}$
H $_{3}$ O $^{+}$ , NO $_{3}^{-}$ and N $_{2}$ O

Answer: A

Explanation.

3 H N O_{2} \to H_{3} O^{+} + N O_{3}^{-} + 2 N O

Step 1: Nitrous acid is unstable and undergoes disproportionation, where nitrogen in

+ 3

oxidation state is both oxidised and reduced. Step 2: Oxidation:

H N O_{2} + H_{2} O \to N O_{3}^{-} + 3 H^{+} + 2 e^{-}

Step 3: Reduction:

H N O_{2} + H^{+} + e^{-} \to N O + H_{2} O

Step 4: Balance electrons: multiply reduction half-reaction by 2 and add to oxidation half-reaction. Step 5:

H N O_{2} + H_{2} O \to N O_{3}^{-} + 3 H^{+} + 2 e^{-}

2 H N O_{2} + 2 H^{+} + 2 e^{-} \to 2 N O + 2 H_{2} O

Step 6: Adding and cancelling:

3 H N O_{2} \to N O_{3}^{-} + H^{+} + 2 N O + H_{2} O

Step 7: Since

H^{+}

in water exists as

H_{3} O^{+}

, the final species are

H_{3} O^{+}

N O_{3}^{-}

, and

N O

A

From NTA/IIT papers: JEE Advanced 2024

Question 4 easy

The setting time of Cement is increased by adding :

Gypsum
Limestone
Clay
Silica

Answer: A

Explanation. **Which cement component sets too fast** Portland cement clinker contains tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite. Of these, **tricalcium aluminate**,

C a_{3} A l_{2} O_{6}

, hydrates almost instantly and would cause *flash setting* - the cement would stiffen before it could be placed. **How gypsum fixes it** About

2 ⁣ - ⁣ 3 %

of **gypsum**,

C a S O_{4} \cdot 2 H_{2} O

, is ground in with the clinker. During hydration it intercepts the tricalcium aluminate and forms ettringite:

C a_{3} A l_{2} O_{6} + 3 C a S O_{4} \cdot 2 H_{2} O + 26 H_{2} O ⟶ C a_{6} A l_{2} (S O_{4})_{3} (O H)_{12} \cdot 26 H_{2} O

Ettringite deposits as a thin protective layer around the cement grains, throttling further attack by water. The setting is therefore **retarded**, i.e. the setting time is increased, giving the mason a workable period. **Why not the others** Limestone

(C a C O_{3})

, clay (the source of silica and alumina) and silica are **raw materials** fed to the kiln to make the clinker in the first place; none of them is added afterwards to control setting. **Answer** The setting time of cement is increased by adding **gypsum** - option **(A)**.

From NTA/IIT papers: JEE Main 2023 · 6 Apr Shift 1

Frequently asked questions

How much of JEE Main comes from Hydrogen s-Block and p-Block Elements?: JEEGenie estimates about 6% of JEE Main marks come from Hydrogen s-Block and p-Block Elements, based on recent papers. The share varies from year to year.
Which formulas matter most in Hydrogen s-Block and p-Block Elements?: The Hydrogen s-Block and p-Block Elements sheet on this page has 13 formula entries, starting with Water Gas Shift Reaction, Hardness of Water Removal, Reaction of Alkali Metals with Water, Thermal Decomposition of Carbonates, Preparation of Borax (Na₂B₄O₇·10H₂O). Each one comes with when to use it and the trap to avoid.
What topics does Hydrogen s-Block and p-Block Elements cover for JEE?: Hydrogen s-Block and p-Block Elements covers Hydrogen and Hydrides, Alkali Metals, Alkaline Earth Metals, Group 13-14 Elements, Group 15-18 Elements, Diagonal Relationship.
How should I revise Hydrogen s-Block and p-Block Elements before the exam?: Learn each formula together with its condition of use, read the trap listed beside it, then practise questions and review every mistake. The practice link on this page opens Hydrogen s-Block and p-Block Elements questions on JEEGenie.
How many previous-year questions are there on Hydrogen s-Block and p-Block Elements?: JEEGenie has 1065 previous-year questions on Hydrogen s-Block and p-Block Elements, and this page shows a few with worked explanations.
Is practice on Hydrogen s-Block and p-Block Elements free on JEEGenie?: Sign-up is free and includes a 7-day Pro trial. After the trial, free accounts keep a limited daily quota.