Nonmetals and Halogens
Nonmetals and Halogens
Nonmetals include hydrogen, carbon, nitrogen, phosphorus, oxygen, sulfur, selenium, the halogens, and the noble gas elements. Hydrogen, oxygen, carbon, and nitrogen are elements found in all living organisms. The study of compound based on carbon and hydrogen and just about all the compounds that make life possible is known as organic chemistry. Nitrogen and the other elements in Group 15 are known as pnictogens. Naturally occurring nitrogen (N2) makes up 78% of the earth’s atmosphere. Because of this ready availability and the requirement for nitrogen by living organisms (as N in proteins), the fixing of nitrogen in forms that may be assimilated by plants (nitrogen fixation) is supremely important. Oxygen and other elements in Group 16 are known as chalcogens. Oxygen-containing compounds comprise 47% of the Earth’s crust. The monoatomic noble gases (Group 18) are colorless, odorless, tasteless, and nonflammable under standard conditions. Because of their very low chemical reactivity, it was originally thought that they cannot combine with those of other elements to form compounds. However, it was later discovered some do indeed form compounds. For example, a large number of xenon compounds have been discovered almost all of which contain the electronegative atoms fluorine or oxygen.
Halogens are the non-metallic elements found in group 17 of the periodic table: and include fluorine, chlorine, bromine, iodine, and astatine. They are the only group whose elements at room temperature include solid, liquid, and gas forms of matter. The chemistry of fluorine, chlorine, bromine, and iodine is perhaps better understood than that of any other group of elements, partly because it is that of singly bonded atoms or single charged anions. These halogens are highly reactive and can combine with many different elements; when they react with metals, they produce a wide range of useful salts. Commercially, halogens are used in disinfectants, lighting, and drug components. Astatine, the heaviest member of the group, is known only in its radioactive form; tennessine, one of the artificially produced 'superheavy' elements, is also radioactive.