Chemistry by Britannica Educational Publishing

Author:Britannica Educational Publishing
Language: eng
Format: epub
ISBN: 978-1-62275-416-8
Publisher: Britannica Educational Publishing
Published: 2015-03-12T04:00:00+00:00

The oxygen people breathe is a molecule that is made of two oxygen atoms. Ozone molecules have three oxygen atoms. Ozone absorbs much of the sun’s ultraviolet radiation and helps to shield living things on Earth from severe ultraviolet-radiation damage. Designua/Shutterstock.com

Six gaseous elements—helium, neon, argon, krypton, xenon, and radon—were thought to be completely inactive chemically when they were first discovered and so were named inert gases. All are present in the air as single, uncombined atoms; thus in their gaseous forms their symbols (for example, He for helium) are written without subscripts. Since the early 1960s chemists have found that under proper conditions at least some of them can be made to form compounds. Today the preferred name of this family of elements is noble gases.

Chemical formulas are also used to represent compounds and their molecular compositions. One atom each of hydrogen and chlorine react to form the compound hydrogen chloride. The chemical formula for hydrogen chloride is HCl. Hydrogen atoms combined with carbon atoms in a proportion of four to one form the flammable gas methane, which is represented as CH4. Three atoms of chlorine combine with one atom of aluminum (Al) to form aluminum chloride (AlCl3), which in a hydrated form (combined with molecules of water) is used in antiperspirants.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.