A compound is a unique substance that forms when two or more elements combine chemically. Compounds form as a result of chemical reactions. The elements in compounds are held together by chemical bonds. A chemical bond is a force of attraction between atoms or ions that share or transfer valence electrons
When 2 or more elements combine a compound stats to form. These are held together with a very strong chemical bond (which can vary depends on the elements). This chemical bond makes all of these little ions come to it and thats how a chemical reaction is made.
At sea level, one square-inch of any surface has about 15 pounds of air sitting on top of it. At 18,000 feet, that same square inch has only 7.5 pounds per square-inch (psi) exerted on it.
