The chemical element hydrogen has the symbol H and the atomic number 1. The lightest element in the periodic table is hydrogen. The simplest member of the chemical family, hydrogen (H), is a colourless, odourless, tasteless, flammable gaseous substance. Hydrogen gas is a loose aggregation of hydrogen molecules, each consisting of a pair of atoms, a diatomic molecule, H2, under normal conditions. The fact that hydrogen burns with oxygen to form water, H2O, is the earliest known important chemical property of hydrogen; indeed, the name hydrogen is derived from Greek words meaning "maker of water."
The alchemist Paracelsus discovered that the bubbles produced when iron filings were added to sulfuric acid were flammable in the early 1500s. Robert Boyle made the same observation in 1671. Because neither of them followed up on their hydrogen discovery, Henry Cavendish gets the credit. He collected the bubbles in 1766 and demonstrated that they were distinct from other gases. He later demonstrated that when hydrogen burns, water is formed, putting an end to the belief that water is an element. Antoine Lavoisier gave the gas the name hydro-gen, which means "water-former."
Harold Urey and his Columbia University colleagues discovered a second, rarer form of hydrogen in 1931. They named it deuterium because it has twice the mass of ordinary hydrogen.
The element hydrogen is by far the most abundant in the universe. It can be found in the sun and most stars, and it makes up the majority of Jupiter's mass.
Hydrogen is found in the most abundant form on Earth as water. It is only found in trace amounts in the atmosphere as a gas – less than 1 part per million by volume. Any hydrogen that does enter the atmosphere is quickly ejected into space by the Earth's gravity.
The majority of hydrogen is created by combining natural gas and steam to form syngas (a mixture of hydrogen and carbon monoxide). The hydrogen is separated from the syngas. The electrolysis of water can also produce hydrogen.
The faint plume of the Space Shuttle Main Engine, compared to the highly visible plume of a Space Shuttle Solid Rocket Booster, which uses an ammonium perchlorate composite, emits ultraviolet light and is nearly invisible to the naked eye with a high oxygen mix. A flame detector may be required to detect a burning hydrogen leak; such leaks can be extremely dangerous. In other circumstances, hydrogen flames are blue, resembling blue natural gas flames. The Hindenburg airship disaster was a well-known example of hydrogen combustion, and the cause is still unknown. Carbon compounds in the airship skin burned, resulting in visible flames in the photographs.
In comparison to diatomic elements like halogens or oxygen, H2 is non-reactive. The very strong H-H bond, with a bond dissociation energy of 435.7 kJ/mol, is the thermodynamic basis for this low reactivity. The nonpolar nature of H2 and its low polarizability are the kinetic basis for its low reactivity. It forms hydrogen chloride and hydrogen fluoride when it reacts spontaneously with chlorine and fluorine, respectively. The presence of metal catalysts has a significant impact on H2 reactivity. In the absence of a catalyst, mixtures of H2 with O2 or air combust readily when heated to at least 500 C by a spark or flame, but they do not react at room temperature.
Many rare earth and transition metals, as well as nanocrystalline and amorphous metals, are highly soluble in hydrogen. Local distortions or impurities in the crystal lattice affect hydrogen solubility in metals.
There are three naturally occurring isotopes of hydrogen:
The most common hydrogen isotope is 1H, which has a 99.98 percent abundance. Because this isotope has only one proton in its nucleus, it is given the descriptive but rarely used formal name protium.
Deuterium is the other stable hydrogen isotope, which has one proton and one neutron in its nucleus. All of the deuterium in the universe is thought to have been created at the Big Bang and has survived since then. Deuterium is not radioactive and poses no significant risk of toxicity.
The nucleus of 3H, also known as tritium, contains one proton and two neutrons. It is radioactive, decaying into helium-3 with a half-life of 12.32 years through beta decay. It is so radioactive that it can be used to make luminous paint, which can be used in watches.
The petrochemical sector
In the "upgrading" of fossil fuels, large amounts of H2 are used. Hydrodealkylation, hydrodesulfurization, and hydrocracking are all major H2 consumers. Many of these reactions are classified as hydrogenolysis, which is defined as the cleavage of carbon bonds.
On a large scale, hydrogenation, or the addition of H2 to various substrates, is carried out. The Haber-Bosch Process uses only a small percentage of the total energy budget in the industry to hydrogenate N2 to produce ammonia. The ammonia produced is used to provide the vast majority of the protein consumed by humans. Unsaturated fats and oils are converted to saturated fats and oils using hydrogenation. The production of margarine is the most common application. Carbon dioxide is hydrogenated to produce methanol. Hydrogen is also obtained from it in the production of hydrochloric acid. H2 is also used in the conversion of some ores to metals as a reducing agent.
Hydrogen is widely used as a generator coolant in power plants due to a number of advantageous properties resulting from its light diatomic molecules. Low density, low viscosity, and the highest specific heat and thermal conductivity of all gases are among these characteristics.
Because there is no naturally occurring source of hydrogen in useful quantities, hydrogen is not an energy resource as a combustion fuel. Nuclear fusion of hydrogen produces the Sun's energy, but this process is difficult to control on Earth. Elemental hydrogen obtained from solar, biological, or electrical sources requires more energy to produce than it does to burn, so it serves as an energy carrier, similar to a battery, in these cases. Hydrogen can be obtained from fossil fuels (such as methane), but these are non-renewable.
In liquid-propellant rockets, such as the Space Shuttle main engines, liquid hydrogen and liquid oxygen are combined as cryogenic fuel.
NICHE AND EVOLVING USES
• Shielding gas: In welding methods such as atomic hydrogen welding, hydrogen is used as a shielding gas.
• Superconductivity studies: Liquid H2 is used in cryogenic research, such as superconductivity studies.
• Buoyant lifting: H2 was once widely used as a lifting gas in balloons and airships because it is lighter than air and has only 7% of the density of air.
• Leak detection: Hydrogen, whether pure or mixed with nitrogen (also known as forming gas), is a tracer gas used to detect minute leaks. The automotive, chemical, power generation, aerospace, and telecommunications industries all have applications. Hydrogen is an approved food additive (E 949) with anti-oxidizing properties and the ability to test food packages for leaks.
• Neutron moderation: Deuterium (hydrogen-2) is used as a neutron moderator in nuclear fission applications.
• Nuclear fusion fuel: In nuclear fusion reactions, deuterium is used as a fuel.
• Isotopic labelling: Deuterium compounds are used in chemistry and biology to investigate the effects of isotopes on reaction rates.
• Rocket propellant: NASA has looked into using atomic hydrogen, boron, or carbon that has been frozen into solid molecular hydrogen particles suspended in liquid helium as a rocket propellant. The mixture vaporises as it warms, allowing the atomic species to recombine and heat the mixture to a high temperature.
• Tritium uses: Tritium (hydrogen-3) is used in the production of hydrogen bombs, as an isotopic label in biosciences, and as a radiation source in luminous paints. It is produced in nuclear reactors.
• Some see hydrogen gas as the clean fuel of the future, as it is made from water and decomposes back into water. Fuel cells powered by hydrogen are increasingly being viewed as "pollution-free" energy sources, and are now being used in some buses and cars.
• Hydrogen is used as a protective atmosphere in the glass industry when making flat glass sheets. It is used as a flushing gas in the electronics industry during the fabrication of silicon chips.
• Hydrogen's low density made it an obvious choice for one of its first practical applications: filling balloons and airships. However, it has a strong reaction with oxygen (forming water), and its use in filling airships came to an end when the Hindenburg caught fire.
• Hydrogen is a necessary component of life. It can be found in water and almost all living things' molecules. Hydrogen, on the other hand, does not play a particularly active role. It remains bonded to carbon and oxygen atoms, while life chemistry occurs at more active sites involving oxygen, nitrogen, and phosphorus, for example.
SAFETY AND PRECAUTIONS
Hydrogen poses a number of risks to human safety, ranging from the potential for detonations and fires when mixed with air to its pure, oxygen-free form being an asphyxiant. Liquid hydrogen is also a cryogen, which poses risks (such as frostbite) associated with extremely cold liquids. Many metals dissolve in hydrogen, which, in addition to leaking out, can have negative consequences such as hydrogen embrittlement, which can lead to cracks and explosions. Leaking hydrogen gas into the atmosphere has the potential to ignite spontaneously. Furthermore, while hydrogen fire is extremely hot, it is almost imperceptible, which can result in accidental burns.