A compound is a substance made from the combination of two or more elements and held together by chemical bonds that are difficult to break. The bonds form as a result of sharing or exchanging electrons among atoms. The smallest unbreakable unit of a compound is a molecule.

  • A compound is formed when different elements react with each other, forming bonds between atoms that produce molecules.  When a compound is exposed to a new element further reactions can take place which produce new compounds.
  • A compound differs from a mixture because the atoms in a mixture are not bonded together. In this case, different elements mix together but no chemical reaction takes place, so each element remains separate and distinct.