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Hydrogen - Notes, Topics, Books, FAQs

Hydrogen - Notes, Topics, Books, FAQs

Edited By Team Careers360 | Updated on Jul 15, 2025 10:21 AM IST

Hydrogen, the lightest and simplest element discovered to date, is composed of a single proton and a single electron. It exists in three isotopic forms: protium, deuterium, and tritium, each distinguished by the number of neutrons in its nucleus. Hydrogen is also an important part of many biomolecules, such as proteins, DNA, carbohydrates, etc. In nature, it is available as natural gas, but in pure form, it is highly inflammable. In the modern periodic table, its position is not fixed because it belongs to the s-block, but its properties resemble those of non-metals.

This Story also Contains
  1. Hydrogen- Important Topics
  2. Various Important Real-life Applications Of Hydrogen:
  3. Overview Of The Chapter
  4. Hydrides
  5. Physical Properties
  6. Chemical Properties
  7. Dihydrogen As a Fuel
  8. How To Prepare For Hydrogen?
  9. Prescribed Books
  10. Some Important PYQs -
  11. Conclusion:
Hydrogen - Notes, Topics, Books, FAQs
Hydrogen - Notes, Topics, Books, FAQs

Hydrogen- Important Topics

Isotopes of Hydrogen:

Hydrogen has three key isotopes—protium (1H), deuterium (2H or D), and tritium (3H or T). All three share the same single-electron configuration but differ in neutron count: protium has none, deuterium has one, and tritium has two neutrons. Tritium is the only radioactive isotope of hydrogen

Dihydrogen:

Dihydrogenis a colorless, odorless, and tasteless gas that burns readily. It is lighter than air and does not dissolve in water. Since hydrogen’s electronegativity falls between that of metals and non-metals, it can behave both as an electron donor (electropositive) and an electron acceptor (electronegative).

Hydrides:

Hydrides are compounds in which hydrogen is chemically bonded to an element that is more electropositive. These substances usually appear as colorless or grayish crystalline solids and are characterized by high melting and boiling points.

Importance Of Water (H2O):

Water is known for having solvent capabilities, and colloquially it is often called the "universal solvent" because it dissolves more substances than any other liquid. Water is neutral in nature. pH of the pure water is 7. It is a weak electrolyte and ionizes into H+ and OH- ions.

Hard Water And Soft Water:

When water has a high concentration of dissolved minerals—mostly calcium and magnesium and when it produces sufficient lather with soap that is called Hard Water And Soft Water respectively.

Hydrogen Peroxide:

Hydrogen Peroxide has a formula H2O2 , it is a colorless, unstable, and highly reactive liquid at room temperature. It is also an important chemical used in pollution control treatment of domestic and industrial effluents.

Various Important Real-life Applications Of Hydrogen:

  • In petroleum refineries, it is used to remove sulfur content. In these plants, it is also used for hydroisomerization.
    Petroleum refineries
  • In ultraviolet lamps, it is used in the form of deuterium. These lamps on heating produce light in the ultraviolet region.
    UV lamps
  • One of the first uses of hydrogen is its use in gas balloons. Due to its light weight, it is used for flying hot balloons.
    Hydrogen baloons

Overview Of The Chapter

Hydrogen is the simplest and lightest element, commonly found as diatomic H₂ gas. It has three isotopes—protium (1H), deuterium (2H), and radioactive tritium (3H)—which differ only in their neutron count. H₂ is colorless, odorless, tasteless, flammable, lighter than air, and barely dissolves in water. It’s produced in labs (such as by reacting zinc with acid) and on an industrial scale using methods like electrolysis or steam reforming. Hydrogen forms ionic, covalent, and metallic hydrides and is widely used in making ammonia and methanol, hydrogenating oils, reducing metal oxides, fueling rockets and fuel cells, and welding. In this article, you will study the various insights about this chapter and preparation tips.

The Position Of Hydrogen In The Periodic Table:

Hydrogen is placed in the first position of the periodic table. However, its actual position is always has been a matter of discussion in science. Its electronic configuration is 1s1, which means either it requires one more electron to completely fulfill the s orbital or it can lose one electron. Thus Hydrogen behaves like alkali metals and halogens. Like alkali metals, Hydrogen forms halides, oxides, and sulfides. But in terms of ionization enthalpy, Hydrogen resembles more to halogens than alkali metals.

Isotopes Of Hydrogen:

As you all must know from your earlier classes, Hydrogen has three isotopes: protium, deuterium and tritium. Protium has no neutron, deuterium has 1 neutron and tritium has 2 neutrons. Since the electronic configuration of all these isotopes is same therefore chemical properties of these isotopes are same. However, their physical properties are considerably different from each other.

Dihydrogen
Dihydrogen is one of the most important chemicals in the universe. It is the most abundant element in the universe with almost 70% mass of the universe. In this section, you will study the preparation of dihydrogen, its properties, and uses.

  • Preparation:
    Hydrogen is prepared by the reaction of granulated zinc with hydrochloric acid or with aqueous alkali.
    $\\*Zn\: +\: 2H^{+}\: \rightarrow \: Zn^{2+}\:+\: H_{2}\\*Zn\: +\: 2NaOH\: \rightarrow \: Na_{2}ZnO_{2}\: +\: H_{2}$
  • Properties of Dihydrogen
    (i) Physical properties:

    (a) It is colourless, tasteless, combustible gas.
    (b) It is almost 1/4 times lighter than air.
    (c) It is very low solubility in water.
    (ii) Chemical Properties:
    The bond dissociation enthalpy of dihydrogen is very high thus, it is very inert at room temperature.

  • Reaction with halogens:
    It reacts with halogens and forms hydrogen halides of the form HX.
    $H_{2}(g)\: +\: X_{2}(g)\: \rightarrow\: 2HX(g)$

  • Reaction with dioxygen:
    It reacts with dioxygen and forms water.
    $2H_{2}(g)\: +\: O_{2}(g)\: \rightarrow\: 2H_{2}O(l)$

  • Reaction with dinitrogen:
    It reacts with dinitrogen and forms ammonia:
    $3H_{2}(g)\: +\: N_{2}(g)\: \rightarrow\: 2NH_{3}(g)$

  • Reaction with metals:
    It reacts with metals and forms hydrides
    $H_{2}(g)\: +\: 2M(g)\: \rightarrow\: 2MH(s)$

  • Uses
    (i) It is used in the synthesis of ammonia.
    (ii) It is used in the manufacture of vanaspati fat.
    (iii) It is used in the production of metal hydrides.
    (iv) It is also used for the synthesis of hydrogen chloride.
NEET Highest Scoring Chapters & Topics
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Hydrides

Water
Water is present on the earth in a tremendous amount. In the human body, it is available up to 70% and in some fruits like watermelon, it is present up to 96%. On earth, it is present in various forms as given in the table:

Source

Total(%)

Oceans

97.33

Saline lakes and inland seas

0.008

Polar ice and glaciers

2.04

Groundwater

0.61

Lakes

0.009

Soil moisture

0.005

Atmospheric water vapour

0.001

Rivers

0.0001


Water has the bent structure with 104.50 bond angle and 2 lone pair of electrons on the oxygen atom. It is a highly polar molecule and forms hydrogen bonding with other water molecules. The structures of water are depicted in fig below:
Tetrahedral structure of water 3d structure of water

Physical Properties

  • It is a colourless liquid.
  • It's melting point is 0oC and boiling point is 100oC.
  • It is an excellent solvent for the transportation of ions and molecules.
  • It has a high heat of vaporization and high heat capacity .
  • It has higher specific heat, thermal conductivity, surface tension, etc.

Chemical Properties

  • Amphoteric nature
    Water is amphoteric in nature. Thus it has the ability to act as an acid as well as a base.
  • Redox reactions with water
    Water is reduced very easily on reacting with highly electropositive metals.
    $2H_{2}O(l)\: +\: 2Na(s)\: \rightarrow \: 2NaOH(aq)\: +\: H_{2}(g)$
  • Hydrolysis reaction
    Some covalent and ionic compounds are hydrolysed in water.
    $\mathrm{P_{4}O_{10}(s)\, +\, 6H_{2}O(l)\, \rightarrow \, 4H_{3}PO_{4}(aq)}$

Hard and Soft Water
When salts of calcium and magnesium are dissolved in the water then it is called as hard water, but when these salts are not present in the water then it is known as soft water. Hard water does not form lather with soaps but soft water forms lather. For washing in hard water, soaps are not efficient and thus we use detergents. With proper water treatment, this hardness of water can be removed.

Hydrogen Peroxide(H2O2)
Hydrogen peroxide is one of the most important compounds which is used in pollution control treatment. Some of the important physical properties of hydrogen peroxide are given in the table below:

Melting Point(K)

272.4

Boiling Point(K)

423

Vapor pressure

1.9

Density

1.64

Dielectric Constant

70.7

Electrical Conductivity

5.1x10-8

  • Preparation: Hydrogen peroxide is prepared by the following methods as discussed below:
    (i) In this method, barium peroxide is treated with sulphuric acid and thus form barium sulphate and hydrogen peroxide.

    $\mathrm{BaO_{2}.8H_{2}O(s)\: +\: H_{2}SO_{4}(aq)\: \rightarrow\: BaSO_{4}(s)\: +\: H_{2}O_{2}(aq)\: +\: 8H_{2}O(l)}$

    (ii) In this method, with the help of electrolytic oxidation of acidified sulfate solutions, peroxodisulphate is obtained. This peroxodisulphate is then hydrolyzed to yield hydrogen peroxide.
    $\mathrm{2HSO_{4}^{-}(aq)\, \overset{Electrolysis}{\rightarrow}\, HO_{3}SOOSO_{3}H(aq)\overset{Hydrolysis}{\rightarrow}\, 2HSO_{4}^{-}(aq)\, +\, 2H^{+}(aq)\, +\, H_{2}O_{2}}$
  • Uses
    (i) In daily life, hydrogen peroxide is used as a hair bleach.
    (ii) It is used in the synthesis of tartaric acid and some food products.
    (iii) It is used a bleaching agent for textiles, leather, fats,etc.
    (iv) It is used to manufacture chemicals like sodium perborate and per-carbonate.

Dihydrogen As a Fuel

Hydrogen gas burns with a high energy output, producing nearly three times the energy of petrol per unit mass. It emits fewer pollutants, with nitrogen oxides being the primary byproduct. This issue can be mitigated by introducing water into the combustion process, lowering the temperature and reducing nitrogen oxide formation.

However, using hydrogen as a fuel presents challenges. Compressed hydrogen cylinders are significantly heavier than petrol tanks, approximately 30 times more. Additionally, liquefying hydrogen requires cooling it to around 20 K, necessitating expensive, insulated storage tanks.

How To Prepare For Hydrogen?

  • Understand the Basics
    Before diving into this chapter, ensure you're familiar with the "Periodic Classification of Elements" as it provides foundational knowledge essential for understanding hydrogen's position and behavior.

  • Focus on Theory
    This chapter is entirely theory-based, making it relatively straightforward. There's no need to memorize complex formulas; instead, concentrate on grasping the concepts and their applications.

  • Practice Regularly
    While the chapter is theory-heavy, practicing related numerical problems can enhance your understanding and retention of the material.

  • Stay Consistent
    Regular study sessions, even if brief, can be more effective than cramming. Consistency helps reinforce learning and improves long-term retention.

  • Use Visual Aids
    Diagrams, charts, and tables can aid in better understanding and memorization of key concepts, such as the preparation methods and properties of hydrogen.

  • Clarify Doubts Promptly
    Don't hesitate to ask teachers or peers about concepts you find challenging. Clearing doubts promptly ensures a solid grasp of the subject matter.

  • Relate to Real-World Applications
    Understanding the practical applications of hydrogen, like its use in fuel cells or the Haber process, can make the theoretical concepts more relatable and easier to comprehend.

Also Read,

Prescribed Books

First, you must finish the class XI and XII NCERT textbook and solve each and every example and unsolved question given in it. Then for advanced level preparation like JEE and NEET, you must follow O.P. Tandon. You must definitely solve the previous year's papers. Meanwhile, in the preparation, you must continuously give the mock tests for the depth of knowledge. Our platform will help you with a variety of questions for deeper knowledge with the help of videos, articles and mock tests.

Some Important PYQs -

Question: $\mathrm{O}-\mathrm{O}$ bond length in $\mathrm{H}_2 \mathrm{O}_2$ is $\underline{\mathrm{X}}$ than the $\mathrm{O}-\mathrm{O}$ bond length in $\mathrm{F}_2 \mathrm{O}_2$. The $\mathrm{O}-\mathrm{H}$ bond length in $\mathrm{H}_2 \mathrm{O}_2$ is $\underline{Y}$ than that of the $\mathrm{O}-\mathrm{F}$ bond in $\mathrm{F}_2 \mathrm{O}_2$.
Choose the correct option for $X$ and $Y$ from those given below:

1) X-shorter, Y - longer

2) X-shorter, Y-shorter

3) X-longer, Y-shorter

4) X-longer, Y-longer

Solution:

$\rightarrow(\mathrm{O}-\mathrm{O}) \mathrm{BL}$ in $\mathrm{H}_2 \mathrm{O}_2$ in longer then $(\mathrm{O}-\mathrm{O}) \mathrm{BL}$ in $\mathrm{O}_2 \mathrm{~F}_2$
$\rightarrow(\mathrm{O}-\mathrm{H}) \mathrm{BL}$ in $\mathrm{H}_2 \mathrm{O}_2$ in shorter than $(\mathrm{O}-\mathrm{F}) \mathrm{BL}$ in $\mathrm{O}_2 \mathrm{~F}_2$
Hence, the answer is the option (3).

Question: Which of the following silicates are used as ion exchangers in softening of hard water:

1) Orthosilicate

2) Zeolite

3) Cyclic silicate

4) Chain silicate

Solution:

Zeolites are 3-D silicates. These are used as ion exchangers in softening of hard water common zeolite is sodium aluminosilicate.

Hence, the answer is the option (2).

Practice more questions from the link given below:

Hydrides - Ionic/Saline Hydride-Practice questions and MCQs Structure of H2O2-Practice questions and MCQs
Softening of Water - Removing Temporary Hardness-Practice questions and MCQs Removal of Permanent Hardness-Practice questions and MCQs

Conclusion:

Hydrogen is the simplest element, made of one proton and one electron, and has three isotopes: protium, deuterium, and tritium. It normally exists as diatomic H₂ gas, which has two nuclear spin forms (ortho and para) and shows traits of both alkali metals and halogens. Hydrogen is prepared in labs (e.g., metal-acid reactions) and industrially (steam reforming). It forms ionic, covalent, and metallic hydrides. Key uses include manufacturing ammonia and methanol, hydrogenating oils, reducing metal oxides, fuel cells, rockets, welding, and supporting water and hydrogen peroxide chemistry.

Frequently Asked Questions (FAQs)

1. How is hydrogen produced?

Hydrogen can be produced through various methods, including:

  • Steam Methane Reforming (SMR): A process that extracts hydrogen from natural gas.
  • Electrolysis: Splitting water into hydrogen and oxygen using electricity.
  • Gasification: Converting organic or fossil-based materials into hydrogen and other products.
  • Biomass Gasification: Producing hydrogen from organic materials through thermal or chemical means.
2. What are the uses of hydrogen?

Hydrogen has numerous applications, such as:

  • Fuel Cells: Providing clean energy for vehicles and stationary power generation.
  • Industrial Processes: Serving as a feedstock in the production of ammonia, petroleum refining, and food processing.
  • Energy Storage: Storing excess renewable energy and supplying it when needed.
  • Metal Processing: Used in various metallurgical processes to remove impurities.
3. Is hydrogen a clean energy source?

Hydrogen can be considered a clean energy source when produced through renewable methods, such as electrolysis powered by solar or wind energy. Fuel cells emitting only water vapor as a byproduct also contribute to reducing greenhouse gas emissions. However, the environmental impact depends on the production method used.

4. Can hydrogen be used as a fuel for vehicles?

Yes, hydrogen can power vehicles equipped with fuel cells, which convert hydrogen and oxygen into electricity to power electric motors. Hydrogen fuel cell vehicles (FCVs) offer a zero-emission alternative to traditional gasoline or diesel vehicles.

5. Why does hydrogen resemble both alkali metals and halogens?

Like alkali metals, it has a 1s¹ electron configuration and forms H⁺ ions. Like halogens, it needs one electron to complete its shell and forms H⁻ or covalent bonds.

6. Why does hydrogen exist as H₂ rather than as individual H atoms?

Hydrogen atoms pair up to form H₂ because sharing two electrons fills their 1s shells, making the molecule more stable—much like achieving a helium-like configuration.

7. How is hydrogen majorly produced in industries?

It’s mainly obtained through steam reforming of natural gas followed by the water–gas shift reaction; electrolysis of water is another method, though less common.

8. How is hydrogen majorly produced in industries?

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Articles

Questions related to

Have a question related to ?

Dear aspirant,

When an electron transitions from the fifth orbit to the ground state in a hydrogen atom, a total of 10 spectral lines can be observed. This is because the electron can make transitions to any lower energy level, including directly to the ground state (n=1), or to intermediate levels (n=2, 3, or 4) before reaching the ground state.

Correct Answer: 1:4


Solution : The correct option is 1:4.

If the density of oxygen is 16 times that of hydrogen, the ratio of their velocities of sound will be the same as the ratio of their densities

The velocity of sound from oxygen to hydrogen is 1:4.

v=√γP/ρ.

  • v is the speed of sound in the gas,
  • γ is the heat capacity ratio 
  • P is the pressure of the gas, and
  • ρ is the density of the gas.

Vo2/VH2 = ρH2/ρO2

√1/16 = 1/4​​.

Question : Comprehension:
Read the given passage carefully and answer the questions that follow.
If you pay close attention to soap advertisements, you may hear of its pH value being claimed to be perfect for human skin. But is there really such a thing? Let's start at the beginning. pH (potential hydrogen) is defined as the concentration of hydrogen ions in a solution. pH values range between 0 and 14.7 is the neutral point, 0 being the most acidic and 14 being the most alkaline. More importantly, your skin isn't exactly pH 5.5; it falls in a range between 4.0 and 7.0, depending on diverse factors like the body part, age, genetics, ethnicity, and environmental conditions.

So, are products formulated at pH 5.5 perfect for skin? The short answer: not really! First, parameters like texture and other ingredients indicate a cleanser's quality, much better than pH alone. Second, though the skin pH rises slightly immediately after cleaning even with plain water, it reverts to its mild acidic pH in an hour. Healthy skin quickly rebalances the 'acid mantle' - a protective layer over the skin—and is unaffected in the long term by the cleanser's pH. Skin modulates pH, making skin products function optimally. So, why market pH 5.5 products as "perfect"? Well, for certain skin types (e.g., oily skin) and certain skin conditions (like acne), an increase in pH can aggravate these skin situations. This might lead to an interpretation that a skin care product needs to be at a pH for optimum cleansing. Hence, skincare experts have expressed reservations about pH being the sole criterion of product safety and 'acid mantle' preservation when factors including plain water may contribute to the same. Thus, an ideal product is almost impossible to define. So, look well beyond pH alone.

Question:
According to the passage, the pH value of human skin is generally:

Option 1: between 7 and 14

Option 2: 5.5

Option 3: between 0 and 7

Option 4: between 4 and 7

Correct Answer: between 4 and 7


Solution : The correct choice is the fourth option.

Explanation: According to the passage, the pH value of human skin is generally in a range between 4.0 and 7.0, depending on various factors like body parts, age, genetics, ethnicity, and environmental conditions.

Therefore, the correct answer is, between 4 and 7.

Correct Answer: Neither I nor II follows


Solution : According to the above-given statement –
Conclusion I: North Korea will declare a state of war against the US and its ally countries soon – Though North Korea has successfully tested a hydrogen bomb, it does not imply that North Korea will declare a state of war as it could be for any other purpose as well.
Conclusion II: The US and its ally countries should not worry about North Korea's successful test of a Hydrogen bomb as it has only increased its nuclear arsenal – It's not confirmed from the above statement that North Korea will never attack the US and its ally countries and this test has only been done to increase its nuclear arsenal. Any motive can be there behind this successful test.

Therefore, the correct answer is neither conclusion I nor conclusion II. Hence, the third option is correct.

Correct Answer: Only II


Solution : The correct option is Only II.

Carbon dioxide (CO2) is classified as an air pollutant when it is found in high concentrations in the Earth's atmosphere, causing harmful impacts on the ecosystem, and climate. Human actions such as fossil fuels, have considerably boosted its concentration. The fundamental issue with increasing CO2 levels as an air pollutant is its role as a greenhouse gas, which leads to global warming.

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