Hydrogen is the most abundant element or chemical substance in our universe, comprising 90% of all atoms. It is the smallest and lightest element, having an atomic number of 1 and an atomic weight of 1.008. Hydrogen is usually found in the form of a gas, and is colorless, odorless, and flammable.

Table of Contents

Position of Hydrogen in Periodic Table

Properties of Hydrogen

Isotopes of Hydrogen

Allotropes of Hydrogen

Different Forms of Hydrogen

Methods of Preparation of Hydrogen

Chemical Reactions of Hydrogen

Uses of Hydrogen

Hydrogen, despite being present in abundance, is rarely found in its free state in nature. It is mostly found in chemical compounds, such as water, where it is bonded to other elements. Interestingly, when hydrogen is burned, it typically reacts with oxygen in the atmosphere to form water. This is why it was named “Hydrogen”, derived from the Greek word “hydro genes” meaning “water creator/former”.

Position of Hydrogen in Periodic Table

Hydrogen is the first element in the periodic table and is located in group 1 and period 1.

Hydrogen is placed at the top of the periodic table due to its similarities to both the Alkali metals of Group I A, and the Halogens of Group VII A.

Similarity to the Alkali Metals Group

1. Both the alkali metals and hydrogen have one electron in their valence shell.

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H (Z = 1) - K1

Li - K2, L1 (Z = 3)

Na (Z = 11) - K2, L8, M1

K$\left(Z = 19\right) - K2, L8, M8, N1$

2. Hydrogen and Elements of IA Group show the same Outer Configuration

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Response:

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H (Z = 1) - 1s1

Li (Z = 3) - 1s², 2s¹

Na (Z = 11) - \1s², \2s², \2p⁶, \3s¹

K (Z = 19) - 1s², 2s², 2p⁶, 3s², 3p⁶, 4s¹

3. Hydrogen also forms halides like alkali metals.

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I-A: NaCl, KBr.

Hydrogen: HCl, HI.

At the Cathode during electrolysis, Hydrogen gas is liberated.

5. The oxidation state of Alkali metals and hydrogen is +1.

Hydrogen Halides undergo ionization in aqueous solution, similar to Alkali Metal Halides.

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Explanation: A database is a collection of organized data that can be easily accessed, managed, and updated. It is used to store and retrieve information, as well as to help keep track of data within an organization.

HCl(aq) ⇄ H+(aq) + Cl–(aq)

NaCl(aq) \rightarrow Na^+(aq) + Cl^-(aq)

7. Hydrogen can form non-metallic compounds with alkali metals.

What is a computer?

Explanation: A computer is a device that can receive, process, store, and output data. It can also be used to control other devices, such as a printer or a robot.

Hydrogen: H2S

I-A: Na_2_S

The Similarities Between Hydrogen and Halogens

1. Both Hydrogen and Halogen (except for Iodine due to its partial metallic character) are non-metals.

2. Hydrogen has a higher electronegativity (2.1).

3. It has a high Ionisation potential.

4. It easily accepts one electron, forming a hydride ion (H–), similar to a halide ion (X–).

5. Both Hydrogen and Halogen can form compounds with both metals and non-metals.

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Halogen: HCl (Hydrogen Chloride; Hydrogen is a non-metal)

Hydrogen: H2S (S is a non-metal)

Thus, hydrogen is more similar to halogen than alkali metals, so its position in the periodic table is not justified.

Similarities Between Alkali Metals and Halogens

It is more electronegative than alkali metals and more electropositive than halogens.

It has only one proton in its nucleus (but no neutrons) and one electron in the extranuclear part.

It forms a neutral oxide.

The sizes of H⁺ and H^- ions are much smaller than those of alkali metals.

The hydrogen ion (H+) is less stable in water compared to Na+ and K+ ions.

Properties of Hydrogen

Physical Properties of Hydrogen

1. Colourless, odourless, neutral gas.

2. Lower solubility in water.

3. Extremely Flammable.

4. Burns with a blue flame.

5. Very low boiling points.

Chemical Properties of Hydrogen

1. The strong bond enthalpy of the H**–**H bond makes dihydrogen relatively inert at room temperature.

2. Atomic hydrogen is produced under a high electric arc.

3. Its orbit contains a single electron, which is incomplete.

4. Hydrogen can form a chemical bond with almost every element.

Isotopes of Hydrogen

Hydrogen has three isotopes:

• Protium
• Deuterium
• Tritium

1. Protium $\left( _{1}^{1}H \right):$ It has zero neutrons.

2. Deuterium (_{1}^{2}H): It has one neutron.

3. Tritium (_{1}^{3}H): It has two neutrons.

Check Out: Detailed information about Isotopes of Hydrogen

Allotropes of Hydrogen

Molecular hydrogen exists in two isomeric forms.

1. Ortho-Hydrogen: In this type, two proton nuclear spins are aligned parallel.

2. Para-Hydrogen: In this type, two proton nuclear spins are aligned in an opposite direction.

#Different Forms of Hydrogen

Atomic Hydrogen:

The reaction of passing molecular hydrogen through an electric arc (2273k) struck between tungsten electrodes is endothermic, and the heat is stored up in the atoms.

2H- Heat

Heat at 2273 K in an electric arc

The liberated hydrogen atoms recombine to form H_2, releasing a large amount of energy which can be utilized for welding purposes.

Nascent Hydrogen:

A form of hydrogen that has recently been released from a compound and has not yet combined with other elements.

Nascent hydrogen is much more reactive and a more powerful reducing agent than ordinary hydrogen, particularly at the moment of its generation when it is first liberated.

The activity of nascent hydrogen is due to its high reactivity and low energy of activation.

Atoms are more reactive than molecules in their atomic state.

Chemical energy released during reaction.

High Internal Pressure due to Nascent Hydrogen Atoms.

Methods of Preparation of Hydrogen

Electrolysis of Water

(\begin{array}{l}2{{H}_{2}}0 + \text{electric current} \rightarrow 2{{H}_{2}}\left( g \right)+{{O}_{2}}\left( g \right)\end{array})

The Reaction of Acids on Strongly Electropositive Metals

\(\begin{array}{l}2Na + {{H}_{2}}SO_{4} \rightarrow {{Na}_{2}}SO_{4} + {{H}_{2}}\end{array}\)

(\begin{array}{l}{2K + 2HCl}\rightarrow{{}}{2KCl + H_2}\end{array})

The Effects of Water on Strongly Electropositive Metals

(\begin{array}{l}2Na + 2{{H}_{2}}O \rightarrow 2NaOH + {{H}_{2}}\end{array})

The Reaction of Alkali on Amphoteric Metals such as Al, Zn, etc.

\( \begin{array}{l} 6 \text{NaOH} + 2 \text{Al} \rightarrow 2 \text{Na}_3 \text{AlO}_3 + 3 \text{H}_2 \end{array} \)

(\begin{array}{l} 2NaOH + Zn \rightarrow N{{a}_{2}}Zn{{O}_{2}},+{{H}_{2}} \underset{Sod.,Zincate}{\mathop{\ }} \end{array})

Large Scale Production of Hydrogen

(\begin{array}{l}C{{H}_{4}} + {{H}_{2}}O \rightarrow[100-1000{}^\circ C]{3-25,bar}CO_{2} + 2{{H}_{2}}\end{array})

(\begin{array}{l}{{H}_{2}}O + CO \rightarrow C{{O}_{2}} + {{H}_{2}}\end{array} )

Preparation of Hydrogen and Its Uses

Chemical Reactions of Hydrogen

Without Oxygen

It reacts with dioxygen (O₂) to form water (H₂O). The reaction is highly exothermic, releasing energy.

(\begin{array}{l}{{H}_{2}} + \frac{1}{2}{{O}_{2}} \xrightarrow[\Delta]{200^\circ C} {{H}_{2}O}\end{array})

Metals

At high temperatures, hydrogen reacts and combines with many metals to form a corresponding hydride.

(\begin{array}{l}2Na + {{H}_{2}} \xrightarrow[\Delta]{350^\circ C} \underset{Sodium,hydride}{\mathop{2NaH}},\end{array} )

Halogens

It reacts with halogens to give hydrogen halides.

(\begin{array}{l}{{H}_{2}} + {{F}_{2}} \xrightarrow{light} 2HF\end{array})

(\begin{array}{l}{{H}{2}} + C{{l}{2}} \xrightarrow{sun,,light} 2HCl\end{array})

(\begin{array}{l}{{H}_2} + B{{r}_2} \xrightarrow{350^\circ C} 2HBr\end{array})

$\begin{array}{l}{H_2} + {I_2} \longrightarrow 2HI\end{array}$

With Dinitrogen

At 73K and 200 atm pressure, dinitrogen forms ammonia.

2NH3(g) $\rightarrow$ 3H2(g) + N2(g) $\Delta H = +92.6\ kJ\ mol^{-1}$

This is the method of manufacture for ammonia via the Haber Process.

Increasing Action

(\begin{array}{l}W{{O}_{3}}+3{{H}_{2}} \rightarrow 3{{H}_{2}}O+W\end{array})

Nuclear Fusion Reactions

It takes place in the stars.

(\begin{array}{l}\underset{Helium}{\mathop{_{2}^{4}He}},+\underset{Position}{\mathop{2{{_{+1}^{0}}^{e}}}},+27M,e,V \rightarrow{{}} 4_{1}^{1}H\end{array} )

Reactions with Organic Compounds:

It reacts with many organic compounds in the presence of catalysts to give useful hydrogenated products of commercial importance. For example,

Hydrogenation of vegetable oils in the presence of a nickel catalyst.

Hydroformylation of olefins to produce aldehydes, which can then be converted into alcohols.

Uses of Hydrogen

Hydrogen has many uses, including:

• Generating electricity
• Fueling vehicles
• Producing fertilizer
• Manufacturing steel
• Creating plastics and other synthetic materials
• Heating homes and buildings

1. Preparing Ammonia

2. As a fuel in the preparation of fuel gases such as water gas.

3. As a reducing agent in metallurgy

4. Nuclear fusion is a process in which a large amount of energy is released in stars.