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Periodic table

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H
H
Hydrogenium

PERIODIC TABLE OF THE ELEMENTS

HYDROGEN

 

 

Atomic number:1

Group numbers:1

Period:1

Electronic configuration:1s1

Formal oxidation number:-1 +1

Electronegativities:2.2

Atomic radius / pm:37.3

Relative atomic mass:1.00794 ± 0.00007

 

Hydrogen was discovered by Sir Henry Cavendish (GB) in 1766. The origin of the name comes from the Greek words hydro and genes meaning water and generate. It is a colourless, odourless gas which burns and forms explosive mixtures in air and reacts violently with oxidants. Hydrogen is the most abundant element in the universe. Commercial quantities of hydrogen are produced by reacting superheated steam with methane or carbon. A laboratory method for producing hydrogen is by the reaction of acids on metals such as zinc or by the electrolysis of water. Most hydrogen is used in the production of ammonia and in metal refining. It is also used as fuel in rockets. Its two heavier isotopes (deuterium and tritium) are used respectively for nuclear fusion.

PHYSICAL PROPERTIES

Density / g dm-3:76.0 (solid, 11 K)

 70.8 (liquid, b.p.)

 0.08988 (gas, 273 K)

Molar volume / cm3mol-1:13.26 (solid, 11 K)

 14.24 (liquid, b.p.)

 22423.54 (gas, 273 K)

Electrical resistivity / μΩcm:- (20 °C)

THERMAL PROPERTIES

Thermal conductivity / W m-1K-1:0.183

Melting point / °C:-259.34

Boiling point / °C:252.87

Heat of fusion / kJ mol-1:0.12

Heat of vaporization / kJ mol-1:0.46

Heat of atomization / kJ mol-1:216.003

IONIZATION ENERGIES

First ionization energy / kJ mol-1:1312.06

Second ionization energy / kJ mol-1:-

Third ionization energy / kJ mol-1:-

ABUNDANCE OF ELEMENTS

in the atmosphere / ppm:0.53

in the Earth's crust / ppm:1400

in the oceans / ppm:(H2O)

CRYSTALLOGRAPHIC DATA

hexagonal

Crystal structure:

hexagonal

Unit-cell dimensions / pm:

a=377.6, c=616.2

Space group:

P63/mmc

ISOTOPES

IsotopeRelative atomic massMass percent (%)
1H1.007825032(1)99.985(1)
2H2.014101778(1)0.015(1)
3H3.016049268(1)*

REDUCTION POTENTIALS

Balanced half-reaction Eo / V
2H+ + 2e- = H2(g)0.000
2H+ + 2e- = H2(g)- 0.41 ([H+] = 10-7 mol dm-3)
2H+ + 2e- = H2(g)- 0.005 (1 mol dm-3 HCl)
2H+ + 2e- = H2(g)- 0.005 (1 mol dm-3 HClO4)
2H2O + 2e- = H2(g) + 2OH-- 0.83
H2O2 + 2H+ + 2e- = 2H2O+1.77
HO2- + H2O + 2e- = 3OH-+0.88
H2(g) + 2e- = 2H-- 2.25

 

PTE <=
1 Hydrogen
 => 2 Helium