Chemical compounds

In chemistry, a chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions.

Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together in a defined spatial arrangement by chemical bonds. 

Atomic model of copper sulphate(II) crystals. image: wikipedia

Chemical compounds can be molecular compounds held together by:

  • covalent bonds, 
  • salts held together by ionic bonds, 
  • intermetallic compounds held together by metallic bonds, 
  • or complexes held together by coordinate covalent bonds. 

Pure chemical elements are not considered chemical compounds, even if they consist of molecules that contain only multiple atoms of a single element (such as H2, S8, etc.), which are called diatomic molecules or polyatomic molecules.