Nascent hydrogen
Encyclopedia
Atomic hydrogen is the species denoted by H (atomic), contrasted with dihydrogen, the usual 'hydrogen' (H2) commonly involved in chemical reactions. It is claimed to exist transiently but long enough to effect chemical reactions. According to one claim, nascent hydrogen is generated in situ
usually by the reaction of zinc
with an acid
, aluminium
(Devarda's alloy
) with sodium hydroxide, or by electrolysis
at the cathode
. Being monoatomic, H atoms are much more reactive and thus a much more effective reducing agent
than ordinary diatomic H2, but again the key question is whether H atoms exist in any chemically meaningful way under the conditions claimed. The concept is more popular in engineering and in older literature on catalysis. Atomic hydrogen is made of individual hydrogen
atoms which are not bound together like ordinary hydrogen into molecules.
to disassociate ordinary H2 hydrogen molecules. When they recombine, they liberate this energy. An electric arc
or ultraviolet
photon
can generate atomic hydrogen.
Atomic hydrogen can be formed under vacuum at temperatures high enough (> 2000 K) to thermally dissociate the molecule, or equivalent excitation in an electric discharge
. Also, electromagnetic radiation above about 11 eV
can be absorbed by H2 and lead to its dissociation.
. Hydrogen is a powerful reducing agent
which eliminates the need for flux
to prevent oxidation of the weld.
Atomic hydrogen determines the frequency of hydrogen maser
s which are used as precise frequency standard
s. They operate at the 1420 MHz frequency
corresponding to an absorption line in atomic hydrogen.
NASA
has investigated the use of atomic hydrogen as a rocket propellant
. It could be stored in liquid helium to prevent it from recombining into molecular hydrogen. When the helium is vaporized, the atomic hydrogen would be released and combine back to molecular hydrogen. The result would be an intensely hot stream of hydrogen and helium gas. The liftoff weight of rockets could be reduced by 50% by this method.
Nascent hydrogen is claimed to reduce nitrite
s to ammonia
, or arsenic
to arsine
even under mild conditions. Detailed scrutiny of such claims usually points to alternative pathways, not H atoms.
in astronomy
at 1420 MHz.
In situ
In situ is a Latin phrase which translated literally as 'In position'. It is used in many different contexts.-Aerospace:In the aerospace industry, equipment on board aircraft must be tested in situ, or in place, to confirm everything functions properly as a system. Individually, each piece may...
usually by the reaction of zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
with an acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
, aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
(Devarda's alloy
Devarda's alloy
Devarda's alloy , is an alloy of aluminium , copper and zinc ....
) with sodium hydroxide, or by electrolysis
Electrolysis
In chemistry and manufacturing, electrolysis is a method of using a direct electric current to drive an otherwise non-spontaneous chemical reaction...
at the cathode
Cathode
A cathode is an electrode through which electric current flows out of a polarized electrical device. Mnemonic: CCD .Cathode polarity is not always negative...
. Being monoatomic, H atoms are much more reactive and thus a much more effective reducing agent
Reducing agent
A reducing agent is the element or compound in a reduction-oxidation reaction that donates an electron to another species; however, since the reducer loses an electron we say it is "oxidized"...
than ordinary diatomic H2, but again the key question is whether H atoms exist in any chemically meaningful way under the conditions claimed. The concept is more popular in engineering and in older literature on catalysis. Atomic hydrogen is made of individual hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
atoms which are not bound together like ordinary hydrogen into molecules.
Making atomic hydrogen
It takes 4.476 eVElectronvolt
In physics, the electron volt is a unit of energy equal to approximately joule . By definition, it is equal to the amount of kinetic energy gained by a single unbound electron when it accelerates through an electric potential difference of one volt...
to disassociate ordinary H2 hydrogen molecules. When they recombine, they liberate this energy. An electric arc
Electric arc
An electric arc is an electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive media such as air. A synonym is arc discharge. An arc discharge is characterized by a lower voltage than a glow discharge, and relies on...
or ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
photon
Photon
In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
can generate atomic hydrogen.
Atomic hydrogen can be formed under vacuum at temperatures high enough (> 2000 K) to thermally dissociate the molecule, or equivalent excitation in an electric discharge
Electric discharge
Electric discharge describes any flow of electric charge through a gas, liquid or solid. Electric discharges include:*Electric glow discharge*Electric arc*Electrostatic discharge*Electric discharge in gases*Leader *Partial discharge...
. Also, electromagnetic radiation above about 11 eV
Electronvolt
In physics, the electron volt is a unit of energy equal to approximately joule . By definition, it is equal to the amount of kinetic energy gained by a single unbound electron when it accelerates through an electric potential difference of one volt...
can be absorbed by H2 and lead to its dissociation.
Uses of atomic hydrogen
The atomic hydrogen torch uses it to generate very high temperatures near 4,000°C for weldingWelding
Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, with pressure sometimes...
. Hydrogen is a powerful reducing agent
Reducing agent
A reducing agent is the element or compound in a reduction-oxidation reaction that donates an electron to another species; however, since the reducer loses an electron we say it is "oxidized"...
which eliminates the need for flux
Flux (metallurgy)
In metallurgy, a flux , is a chemical cleaning agent, flowing agent, or purifying agent. Fluxes may have more than one function at a time...
to prevent oxidation of the weld.
Atomic hydrogen determines the frequency of hydrogen maser
Hydrogen maser
A Hydrogen maser, also known as hydrogen frequency standard, is a specific type of maser that uses the intrinsic properties of the hydrogen atom to serve as a precision frequency reference....
s which are used as precise frequency standard
Frequency standard
A frequency standard is a stable oscillator used for frequency calibration or reference. A frequency standard generates a fundamental frequency with a high degree of accuracy and precision. Harmonics of this fundamental frequency are used to provide reference points.Since time is the reciprocal of...
s. They operate at the 1420 MHz frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
corresponding to an absorption line in atomic hydrogen.
NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
has investigated the use of atomic hydrogen as a rocket propellant
Rocket propellant
Rocket propellant is mass that is stored in some form of propellant tank, prior to being used as the propulsive mass that is ejected from a rocket engine in the form of a fluid jet to produce thrust. A fuel propellant is often burned with an oxidizer propellant to produce large volumes of very hot...
. It could be stored in liquid helium to prevent it from recombining into molecular hydrogen. When the helium is vaporized, the atomic hydrogen would be released and combine back to molecular hydrogen. The result would be an intensely hot stream of hydrogen and helium gas. The liftoff weight of rockets could be reduced by 50% by this method.
Nascent hydrogen is claimed to reduce nitrite
Nitrite
The nitrite ion has the chemical formula NO2−. The anion is symmetric with equal N-O bond lengths and a O-N-O bond angle of ca. 120°. On protonation the unstable weak acid nitrous acid is produced. Nitrite can be oxidised or reduced, with product somewhat dependent on the oxidizing/reducing agent...
s to ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
, or arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
to arsine
Arsine
Arsine is the chemical compound with the formula AsH3. This flammable, pyrophoric, and highly toxic gas is one of the simplest compounds of arsenic...
even under mild conditions. Detailed scrutiny of such claims usually points to alternative pathways, not H atoms.
In nature
Most interstellar hydrogen is in the form of atomic hydrogen because the atoms can seldom collide and combine. They are the source of the important 21 cm hydrogen lineHydrogen line
The hydrogen line, 21 centimeter line or HI line refers to the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms. This electromagnetic radiation is at the precise frequency of 1420.40575177 MHz, which is equivalent to the vacuum...
in astronomy
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
at 1420 MHz.
Another meaning
Occasionally, hydrogen chemisorbed on metal surfaces is referred to as "nascent", although this terminology is fading with time. Other views hold that such chemisorbed hydrogen is "a bit less reactive than nascent hydrogen because of the bonds provided by the catalyst metal surface". Also, such catalyst provided atoms are not called nascent hydrogen, because they do not need to be captured and reacted in their instantaneous, temporary, "just generated" state, because the catalyst is able to reversibly generate them from the hydrogen gas supply at any time.See also
- Nascent state (chemistry)Nascent state (chemistry)Nascent state or in statu nascendi , in chemistry, refers to the form of an chemical element in the instance of their liberation or formation. Often encountered are atomic oxygen , nascent hydrogen , and similar forms of chlorine or bromine...
- Cold fusionCold fusionCold fusion, also called low-energy nuclear reaction , refers to the hypothesis that nuclear fusion might explain the results of a group of experiments conducted at ordinary temperatures . Both the experimental results and the hypothesis are disputed...
- Devarda's alloyDevarda's alloyDevarda's alloy , is an alloy of aluminium , copper and zinc ....
- Marsh testMarsh testThe Marsh test is a highly sensitive method in the detection of arsenic, especially useful in the field of forensic toxicology when arsenic was used as a poison...
- ArsineArsineArsine is the chemical compound with the formula AsH3. This flammable, pyrophoric, and highly toxic gas is one of the simplest compounds of arsenic...
- StibineStibineStibine is the chemical compound with the formula SbH3. This colourless gas is the principal covalent hydride of antimony and a heavy analogue of ammonia. The molecule is pyramidal with H–Sb–H angles of 91.7° and Sb–H distances of 1.707 Å...
- James Marsh
- Arsine
- Lithium aluminium hydrideLithium aluminium hydrideLithium aluminium hydride, commonly abbreviated to LAH or known as LithAl, is an inorganic compound with the chemical formula LiAlH4. It was discovered by Finholt, Bond and Schlesinger in 1947. This compound is used as a reducing agent in organic synthesis, especially for the reduction of esters,...
- Lithium borohydrideLithium borohydrideLithium borohydride is a tetrahydroborate and known in organic synthesis as a reducing agent for esters. Although less common than the related sodium borohydride, the lithium salt offers some advantages of being highly soluble in ethers and being a stronger reducing agent but still safer to...
- Sodium borohydrideSodium borohydrideSodium borohydride, also known as sodium tetrahydridoborate, is an inorganic compound with the formula NaBH4. This white solid, usually encountered as a powder, is a versatile reducing agent that finds wide application in chemistry, both in the laboratory and on a technical scale. Large amounts are...