Hydrogen

Hydrogen

Hydrogen is a tasteless, odorless, colorless gas. Hydrogen is found in group 1 and period 1 on the periodic table. Hydrogen is classified as a nonmetal on the periodic table. The symbol for hydrogen is represented by an H, its atomic number is 1, and its atomic weight is 1.0079. The hydrogen atom consists of one proton, which has a positive charge, and one electron, which has a negative charge. The term hydrogen comes from two Greek words meaning water-former. Henry Cavendish, an English scientist, discovered it in 1766. Named by Lavoisier, hydrogen is the most abundant of all elements in the universe. The sun and many other stars consist of mostly hydrogen. It is the third most abundant element on earth. It is estimated that hydrogen makes up more than 90% of all the atoms or three quarters of the mass of the universe. Hydrogen plays an important part in powering the universe though both the proton-proton reaction and carbon-nitrogen cycle. Hydrogen occurs in almost all organic compounds. Many of the compounds found in plant and animal tissues are organic. Production of hydrogen in the U.S. alone now amounts to about 3 billion cubic feet per year. Some of the methods that hydrogen is prepared by are steam on heated carbon, decomposition of certain hydrocarbons with heat, action of sodium or potassium hydroxide on aluminum, or displacement from acids by certain metals. Hydrogen may be condensed to a liquid that boils at -257.87oC and freezes at -259.14oC. Hydrogen gas has the lowest density of any known substance. At 20oC, the gas has a density of 0.00008375 gram per cubic cm. Hydrogen gas is only slightly soluble in water. It is not poisonous. Hydrogen has three isotopes called protium, deuterium, and tritium. Tritium is radioactive and has been uses in the hydrogen bomb. In the laboratory, hydrogen can be produced by the electrolysis of water. Hydrogen combines directly with several of the most active elements, but most hydrogen compounds are made by indirect methods. Mixtures of hydrogen and oxygen explode violently when ignited by a spark. When there is air or oxygen with hydrogen's presence, hydrogen burns with a hot flame and forms water. Chlorine burns in hydrogen and forms a colorless gas called HCl. Ammonia, whose symbol is NH3, is made by combining hydrogen and nitrogen. Other hydrogen compounds prepared indirectly include hydrogen peroxide (H2O2), acetic