Laura Vidal Juan
• Etymology: the name of an element.
• Hydrogen is the chemical element with atomic number 1. It
is represented by the symbol H.
• Its atomic mass is 1.00794 amu (hydrogen is the lightest
• Hydrogen is the most abundant of the chemical elements,
constituting roughly 75% of the universe's elemental mass
• Elemental hydrogen is relatively rare on Earth, and is
industrially produced from hydrocarbons
• T. Von Hohenheim = Paracelsus (1493–1541) produced H2
artificially via the mixing of metals with strong acids.
• Robert Boyle (1671) rediscovered and described the reaction
between iron filings and dilute acids, which results in the production
of hydrogen gas.
• Henry Cavendish (1766) recognized hydrogen gas as a discrete
substance, by identifying the gas from a metal-acid reaction as
"inflammable air" and further finding that the gas produces water
• Antoine Lavoisier (1783) gave the element the name of hydrogen
when he (with Laplace) reproduced Cavendish's finding.
• Study of the energetics and bonding of the hydrogen atom by
Maxwell, has played a key role in the development of quantum
• Bonded to fluorine, oxygen, or
nitrogen it forms hydrogen bonding.
• With metals and metalloids it forms
hydrides, that could be implied in
• With carbon it forms organic
compounds: importance in
• H+ is implied in acid-base chemistry.
• H2 is a product of some types of anaerobic metabolism and it is
produced by several microorganisms.
• It take part in redox reactions
• H2 is created during pyruvate fermentation to water.
• Water splitting, that occurs during photosintesis, give rise to H+.
• H+ is important in the electronic transfer chain.
• Hydrogen is highly soluble in many compounds of rare
earth metals and transition metals and can be dissolved
in crystalline and amorphous metals.
• It is highly flammable and will burn at concentrations as
low as 4% H2 in air.
• It ignites automatically at a temperature of 560 °C.
• H2 reacts directly with other oxidizing elements.
• Pure hydrogen-oxygen flames burn in the ultraviolet
color range and are nearly invisible to the naked eye.
General: At standard temperature and pressure, hydrogen is a
colorless, odorless, nonmetallic, tasteless, highly flammable
diatomic gas with the molecular formula H2.
Density = 0.08988 g/L Heat of fusion = 117 kJ·mol−1
Melting point = 14.01 K Heat of vaporization = 0.904 kJ·mol−1
Boiling point = 20.28 K It has the highest thermal conductivity of any gas
Crystal structure = hexagonal
Atomic radius = 25 pm
Electronegativity = 2.1
• One of the first uses of H2 was for balloons, and later airships.
Infamously, H2 was used in the Hindenburg airship that was
destroyed in a midair fire.
The highly flammable hydrogen (H2) was later
replaced for airships and most balloons by the
unreactive helium (He).
• Uses in petroleum and chemical industries: processing of fossil fuels, and in
the production of ammonia.
• Uses as a reactant: hydrogenating agent (in increasing the level of saturation
of unsaturated fats and oils ); in the production of methanol; in the
manufacture of hydrochloric acid; reducing agent of metallic ores.
• Applications in physics and engineering: shielding gas in
welding methods, the rotor coolant in electrical generators
at power stations
• Liquid H2 is used in cryogenic research
• As a tracer gas for minute leak detection
• Isotopes: Protium is the most common isotope; Deuterium
(hydrogen-2) is used in nuclear fission application; Tritium
(hydrogen-3), produced in nuclear reactors, is used in the
production of hydrogen bombs, as an isotopic label in the
biosciences, and as a radiation source in luminous paints.