Hydrogen is one of the three most abundant elements present on Earth. It was discovered in 1766 by Henry Cavendish and is widely used for various industrial, medical and recreational purposes.
Discovery and History
The informal discovery of hydrogen dates to 1500s when Paracelsus (alchemist) observed the production of bubbles (gas) when sulfuric acid was added to iron and later Robert Boyle (1671) observed the production of same flammable bubbles. But the formal discovery of hydrogen was reported by Henry Cavendish (1766), who analyzed the bubbles and showed that burning of hydrogen lead to the production of water. Hence the gas was named hydro-genes (1783 by Antoine Lavoisier), which is the Greek word for “water-former”. In 1898, James Dewar successfully liquified hydrogen . In as early as 1783, hydrogen gas was used in air balloons by Jacques Charles, which demonstrated the power and reliability of hydrogen for providing the lift for air-travel. And later, Henri Giffard (1852), made the first hydrogen-lifted airship. Hydrogen-lifted airships found tremendous usage in the World War 1, where they were used for transferring people, as observation platforms and as bombers. Hydrogen also has a notorious event related to its name, the incident of Hindenburg airship (1937), were combustion of hydrogen led to the destruction of the ship in the midair and brought an end to the era of hydrogen-based air-travels .
|Periodic Table Classification||Group 1
|State at 20C||Gas|
|Density||0.09 g.cm-3 at 20°C|
|Atomic Mass||1.01 g.mol -1|
|Electronegativity according to Pauling||2.20|
Hydrogen is ubiquitous in nature as it is present in water. It is considered as the 3rd most abundant element in the Earth’s atmosphere and the most abundant element in the universe. Hydrogen is the main component of living systems (hydrocarbons). . Hydrogen is found in significant abundance in undetected form of mass, such as dark matter, and in gas giant planets and stars. In gaseous form, it is present only in a small fraction and makes around 1 part per million in volume. Hydrogen is mostly present in its atomic and plasma states, which have significantly different properties as compared to the molecular (gaseous) form. In its plasma form, hydrogen give rise to natural phenomenon of Birkeland currents and aurora (by interacting with magnetosphere of the Earth). The neutral atomic state of hydrogen is mainly present in the interstellar medium ISM (outer space) .
Hydrogen gas is the lightest of all gases. It has the lowest density (0.0899*10 -3 g.cm -3 at 20 °C) as compared to all other gases. Hydrogen is odorless and colorless gas. It is non-toxic and nonmetallic at standard conditions (standard temperature and pressure). Hydrogen has an atomic number of 1 and atomic mass of 1.007825g.mol-1. It has a boiling point of -252.8C and a melting point of -259.2 C.
Hydrogen is a highly (combustible) flammable gas. Hydrogen is more soluble in organic solvents and less soluble in water. At room temperature, hydrogen is stable and unreactive. However, under different environmental conditions, various metals absorb hydrogen, such as the absorption of hydrogen by steel can cause brittleness in steel . Hydrogen becomes highly reactive at higher temperatures. And lead to the dissociation of its diatomic form into free atom of hydrogen, which is highly reactive and a powerful reducing agent. Free hydrogen radical can react with chlorides and oxides of various metals to form free metals. It can lead to the formation of hydrides of various metals, non-metals such as, H2S, NAH, PH3 and KH. One of the most common compounds produced by elemental hydrogen is hydrogen peroxide (H2O2) with oxygen. The light atomic nature of hydrogen impart various favorable properties to it, including low viscosity, and high thermal conductivity and specific heat as compared to all other gases.
Significance and Uses
- Hydrogen is widely used to produce ammonia.
- The reaction of combination of hydrogen atoms is quite exothermic. And this heat is used in atomic hydrogen welding process.
- Hydrogen is widely used for the catalytic hydrogenation process, which is used in the production of vegetable ghee from vegetable oil (unsaturated fats to saturated fats).
- Hydrogen is becoming popular as green fuel (clean fuel, with no emission of carbon dioxide or other toxic compounds). Various fuel cells are being manufactured for making internal combustion engines for making pollution free buses and cars.
- Hydrogen is used as rocket fuel and as rocket propellent.
- Hydrogen provides protective and stable atmosphere for the production of flat glass sheets in glass industry.
- It is used in electronic industry for the manufacturing of silicon chips (as flushing gas).
- Hydrogen is widely used in power stations as a coolant in generators.
Health Effects of Hydrogen Gas
Hydrogen is toxic to the body and can absorbed by inhalation which can lead to oxygen deficiency in the body. affected individuals lead to hypoxia and show symptoms such as headaches, dizziness, ringing in ears, nausea, vomiting and unconsciousness. If untreated, victim can turn blue and it can be fatal. When hydrogen is exposed to air, it can lead to formation of explosive mixtures. Heating of hydrogen can also cause violent combustion or explosion .
Isotopes of Hydrogen
There are three naturally occurring isotopes of hydrogen, named 1H (protium), 2H (deuterium), and 3H (tritium). Protium is the most abundant hydrogen isotope (99.98%). Tritium is the most stable radioisotope and have a half-life of 12.32 years. All heavier isotopes of hydrogen are synthetic and are extremely unstable. Deuterium has found major applications in nuclear magnetic resonance studies .
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