Michael G. answered 08/20/22
Effective Ph.D. Tutor for Microbiology and Molecular Biology
A compound is a substance formed when atoms of 2 or more elements are held together by some type of chemical bond. Water is a compound because it cannot be subdivided into water atoms. It only exists as a molecule made of 2 hydrogen atoms linked to 1 oxygen atom through polar covalent bonds. Air is a mixture of various gases of varying concentrations; it's composition is not "consistent." Steel is a mixture of iron and carbon. Carbon is a simple element.