HYDROGEN

Laura Vidal Juan

INTRODUCTIONINTRODUCTION• 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 element).

• 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

DISCOVERYDISCOVERY

• 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 when burned.

• 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 mechanics.

COMPOUNDSCOMPOUNDS

• Bonded to fluorine, oxygen, or nitrogen it forms hydrogen bonding.

• With metals and metalloids it forms hydrides, that could be implied in coordination complex.

• With carbon it forms organic compounds: importance in Biochemistry.

• H+ is implied in acid-base chemistry.

BIOHYDROGENBIOHYDROGEN

• H2 is a product of some types of anaerobic metabolism and it is produced by several microorganisms.

• It take part in redox reactions

(hydrogenases).

• 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.

CHEMICAL CHARACTERISTICSCHEMICAL CHARACTERISTICS

• 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.

SOME PROPERTIESSOME PROPERTIES General: At standard temperature and pressure, hydrogen is a colorless,

odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H2.

Physical properties:

Atomic properties: Crystal structure = hexagonal Atomic radius = 25 pm Electronegativity = 2.1

Heat of fusion = 117 kJ·mol−1 Heat of vaporization = 0.904 kJ·mol−1 It has the highest thermal conductivity of any gas

Density = 0.08988 g/L Melting point = 14.01 K Boiling point = 20.28 K

APPLICATIONS IAPPLICATIONS I• 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 IIAPPLICATIONS II

• 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.