| Atomic Number: | 1 | Atomic Symbol: | H |
| Atomic Weight: | 1.0079 | Electron Configuration: | 1 |
| Shells: | 1 | Filling Orbital: | 1s |
| Melting Point: | -259.14oC | Boiling Point: | -252.87oC |
| Uses: | Rocket Fuel, in ballons, metal refining etc. |
History
(Gr. hydro, water, and genes, forming) Hydrogen was prepared
many years before it was recognized as a distinct substance by Cavendish in
1776.
Named by Lavoisier, hydrogen is the most abundant of all elements in the
universe, and it is thought that the heavier elements were, and still are, being
built from hydrogen and helium.
Sources
Hydrogen is estimated to make up more than 90% of all the atoms
or three quarters of the mass of the universe. This element is found in the sun
and most stars, and plays an important part in the proton-proton reaction and
carbon-nitrogen cycle, which accounts for the energy of the sun and stars.
Hydrogen is thought to be a major component of Jupiter and that at some depth
in the planet's interior the pressure is so great that solid molecular hydrogen
is converted to solid metalic hydrogen.
In 1973, a group of Russian experimenters may have produced metallic hydrogen
at a pressure of 2.8 Mbar. At the transition the density changed from 1.08 to
1.3 g/cm^3. Earlier, in 1972, a Livermore, California, group also reported on a
similar experiment in which they observed a pressure-volume point centered at 2
Mbar. Predictions say that metallic hydrogen may be metastable; others have
predicted it would be a superconductor at room temperature.
Compounds
On earth, hydrogen occurs chiefly in combination with oxygen
in water, but it is also present in organic matter such as living plants,
petroleum, coal, etc. It is present as the free element in the atmosphere, but
only to the extent of less than 1 ppm by volume. The lightest of all gases,
hydrogen combines with other elements -- sometimes explosively -- to form
compounds.
Uses
Great quantities are required commercially for the fixation of
nitrogen from the air in the Haber ammonia process and for the hydrogenation of
fats and oils. It is also used in large quantities in methanol production, in
hydrodealkylation, hydrocracking, and hydrodesulfurization. Other uses include
rocket fuel, welding, producing hydrochloric acid, reducing metallic ores, and
filling baloons.
The lifting power of 1 ft3 of hydrogen gas is about 0.07 lb at 0C,
760 mm pressure. Production of hydrogen in the U.S. alone now amounts to about 3
billion cubic feet per year. Hydrogen is prepared by
- steam on heated carbon,
- decomposition of certain hydrocarbons with heat,
- action of sodium or potassium hydroxide on aluminum
- electolysis of water, or
- displacement from acids by certain metals.
Liquid hydrogen is
important in cryrogenics and in the study of superconductivity, as its melting
point is only 20 degrees above absolute zero.
Tritium is readily produced in nuclear reactors and is used in the production
of the hydrogen bomb. It is also used as a radioactive agent in making luminous
paints, and as a tracer.
Consideration is being given to an entire economy based on solar- and
nuclear-generated hydrogen. Public acceptance, high capital investment, and the
high cost of hydrogen with respect to today's fuels are but a few of the
problems facing such an econonomy.
Located in remote regions, power plants would electrolyze sea water; the
hydrogen produced would travel to distant cities by pipelines. Pollution-free
hydrogen could replace natural gas, gasoline, etc., and could serve as a
reducing agent in metallurgy, chemical processing, refining, etc. It could also
be used to convert trash into methane and ethylene.
Cost
The current price of tritium, to authorized personnel, is about
$2/Ci; deuterium gas is readily available, without permit, at about $1/l.
Heavy water, deuterium oxide (D2O), which is used as a moderator to slow down
neutrons, is available without permit at a cost of 6c to $1/g, depending on
quantity and purity.
Forms
Quite apart from isotopes, it has been shown that under ordinary
conditions hydrogen gas is a mixture of two kinds of molecules, known as ortho-
and para-hydrogen, which differ from one another by the spins of their electrons
and nuclei.
Normal hydrogen at room temperature contains 25% of the para form and 75% of
the ortho form. The ortho form cannot be prepared in the pure state. Since the
two forms differ in energy, the physical properties also differ. The melting and
boiling points of parahydrogen are about 0.1C lower than those of normal
hydrogen.
Isotopes
The ordinary isotope of hydrogen, H, is known as Protium, the
other two isotopes are Deuterium and Tritium. Hydrogen is the only element whose
isotopes have been given different names. Deuterium and Tritium are both used as
fuel for nuclear fusion reactors. One atom of Deuterium is found in about 6000
ordinary hydrogen atoms.
Deuterium is used as a moderator to slow down neutrons. Tritium atoms are
also present but in much smaller proportions. Tritium is readily produced in
nuclear reactors and is used in the production of the hydrogen (fusion) bomb. It
is also used as a radioactive agent in making luminous paints, and as a tracer.