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H¹
H' at. wt. (natural) 1.007967 at. wt. (H') 1.007822 at. no. 1 m.p. - 259.14°C b.p. - 252.87°C density 0.08988 gm./l density (liquid) 70.8 gm/i. (-253° C) density (solid) 7016 gm/i. (-262° C) valence 1.
| SHELL | K | L | M | N | O | P | Q |
| SUB SHELL | He | Neon | Argon | Krypton | Xenon | Radon | Eka-radon |
| 1s | 2s 2p | 3s 3p | 3d 4s 4p | 4d 5s 5p | 4f 5d 6s 6p | 5f 6d 7s 7p | |
| Hydrogen | 1s1 | ||||||
| Symbol | 2S½ | ||||||
Hydrogen was prepared many years before it was recognized as a distinct substance by Cavendish in 1766. It was 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. It has leeen estimated that hydrogen makes up more than 90% of all the atoms or three-quarters of the mass of the universe. It 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. It is thought that hydrogen is a major component of the planet Jupiter and that at some depth in the planet's interior the pressure is so great that solid molecular hydrogen is converted into solid metallic hydrogen. This transition is thought to take place at a pressure of one megabar. Ultimately it may he possible to produce metallic hydrogen in the laboratory. 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 pnesent as the free element in the atmosphere, but only to the extent of less than I part/million, by volume. It is the lightestof all gases, and combines with other elements, sometimes explosively, to form compounds. Great quantities of hydrogen 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 farge quantities in methanol production, in hydrodealkylation, hydrocracking, and hy- drodesulfurization. It is also used as a rocket fuel, for weld- ing, for production of hydrochloric acid, for the reduction of metallic ores, and for filling balloons. The lifting power of 1 cu. ft. of hydrogen gas is about 0.076 lb. at 00C, 760 mm pressure. Production of hydrogen in the U.S. alone now amounts to hundreds of milli6ns of cubic feet per day. It is prepared by the action of steam on heated carbon, by decomposition of certain hydrocarbons with heat, by the electrolysis of water, or by the displacement from acids by certain metals. It is also produced by the action of sodium or potassium hydroxide on aluminum. Liquid hydrogen is important in cryogenics and in the study of superconduc- tivity as its m.p. is only a few degrees above absolute zero. The ordinary isotope of hydrogen, 1H' is known asprotium. In 1932 Urey announced the preparation of a stable isotope, deuterium, with an atomic weight of2 (1H2 or D). Two years later an unstable isotope, tritium (1H3) with an atomic weight of 3 was discovered. Tritium has a half~life of about 12.5 years. One part deuterium is found to about 6000 ordinary hydrogen atoms. Tritium atoms are also present but in much smaller proportion. 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. The current price of tritium, to authorized personnel, is about $2/curie; deuterium gas is readily available, without permit, at about $1/liter. Heavy water, deuterium oxide (D20), which is used as a moderator to slow down neutrons, is available without permit at a cost of 6~ to 31/gm., depending on quantity and purity. Quite apart from isotopes, it has been shown that hydrogen gas under ordinary conditions 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 para-hydrogen are about 0.1 0C lower than those of normal hydrogen. Of current interest is a newly discovered form of water, a polymer, known as polywater.
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