Latin nameHydrogenium
English nameHydrogen
chemical symbolH
atomic number1
relative atomic mass 1,00794
discovery date1766
discovererH. Cavendish
melting point [°C]-255,34
boiling point [°C]-255,87
critical temperature [°C]-240,18
ignition temperature [°C]580
critical pressure [MPa]1,293
density [g cm-3]0,00008988
electronegativity [Pauling]2,2
oxidation states-I, I
electron configuration1s1
atomic radius [pm]53
covalent radius [pm]37
specific heat [J g-1K-1]14,304
heat of fusion [kJ mol-1]0,05868
thermal conductivity [W m-1 K-1]0,1805
1. ionizing energy [kJmol-1]1312,049
state at normal conditionsgas

Chemical Properties

Hydrogen is a colorless, tasteless and odorless diatomic, light, flammable gas. Creates diatomic molecules that contain simple covalent σ-bond. Monoatomic nascent hydrogen is strongly reactive. Molecular hydrogen under normal temperature reacts only with fluorine and chlorine. Fired hydrogen reacts with oxygen to form water. Under suitable conditions, hydrogen is directly combines with sulfur, bromine and iodine.

In the compounds of features in the oxidation state I, is always combined with the alkali metals and alkaline earth metals occurs hydrogen in the oxidation state -I. To these elements, therefore, the hydrogen acts as an oxidising agent.

Almost all the elements form hydrides with different bond type. The alkali metals and alkaline earth metals are colorless solid reactive ion hydrides, with transition metals form metal hydrides, with the other elements formed of liquid or gaseous hydrides covalent or transient.

Occurrence in nature

The naturally occurring hydrogen bound in water and a huge amount of organic compounds. Significant hydrogen is represented in the form of crystalline, constitutive or free water in many minerals. Small amounts of elemental hydrogen is in the high layers of the atmosphere.

The proportion of hydrogen in the earth's crust is 0.88% wt. In the universe, hydrogen is the most common element. Natural hydrogen is a mixture of three isotopes. The highest proportion (99.985%) is the isotope 1H - protium, 0.015% for the 2H isotope - deuterium and 0.0001% belong radioactive isotope 3H - tritium. Half-life of tritium is 12.26 years.

Hydrogen Production

Large-scale industrial production of hydrogen is currently the most frequently performed catalytic steam reforming of natural gas and other light hydrocarbons, partial oxidation of heavy residues from the distillation of crude oil or water gas conversion.