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Chemistry LibreTexts

1A.5: Compounds

  • Page ID
  • Learning Objectives

    • Define compound
    • Recognize the different types of compounds (ionic and molecular compounds)


    Compounds occur when two or more atoms combine into a pure substance. These can be broken down into their constituent atoms. In chemical reactions the atoms of the reactants interact to form new substances. The reacting species are called reactants, and those produced are products. Reactant and products can be either elements or compounds. Compounds are held together by chemical bonds.

    The following video shows the formation of the compound, Sodium Chloride from the elements sodium and chloride from Nile Red's YouTube Channel.

    Video \(\PageIndex{1}\): Youtube showing the formation of an ionic compound from its constituent elements. Uploaded by NileRed (

    What is the difference between CO and Co?

    The first letter of an element must be capitalized and the second is never capitalized. CO is the compound carbon monoxide, Co is the element cobalt.

    Are all compounds molecules?

    No, molecules are discrete entities where two or more nuclei from different atoms have shared electrons, and this type of bond is called a covalent bond. Water (H2O ) is a molecule with an oxygen connected to two different hydrogens through covalent bonds. Another common type of compound is an ionic compound like sodium chloride or table salt, NaCl. Ionic compounds form crystal lattices with each positive ion (cation) surrounded by multiple negative ions (anions).

    Are all compounds either molecules or ionic compounds?

    No, although in this class we will focus on ionic and molecular compounds. But there are many types of forces holding chemical species together. Metals have metalic bonds which can be of either the same element, or between different elements (brass metal is alloy, a mixture of zinc and copper held together through metallic bonds.) Ice is water held together through intermolecular forces. Diamond is a covalent network of carbon atoms (each carbon atom within the interior of the diamond is connected to 4 other carbon atoms) and there is no real formula, as the number of carbon atoms depends on the size of the diamond.

    Contributors and Attributions

    Robert E. Belford (University of Arkansas Little Rock; Department of Chemistry). The breadth, depth and veracity of this work is the responsibility of Robert E. Belford, You should contact him if you have any concerns. This material has both original contributions, and content built upon prior contributions of the LibreTexts Community and other resources, including but not limited to:

    • Ronia Kattoum (Learning Objectives)