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Covalent Bonding - Drawing and Explanation

Chemistry Core with Orlando Broomfield

Learning Goals

  • Describe how covalent bonds are formed.
  • Use dot-cross diagrams to illustrate the bonding in covalent compounds.
  • Outline the properties of simple molecules

Covalent Bonding

  • Covalent bonds occur between nonmetals, which could be of the same element, or different elements.
  • The atoms involved in a covalent bond share one or more electron pair(s).
  • Covalent bonding is the electrostatic force of attraction between the nuclei of the non-metallic atoms and their shared pairs of electrons.
  • Atoms participate in sharing electron pairs, to gain a stable electronic configuration. 

Formation of Covalent Bonds

  • We draw dot and cross diagrams with overlapping valence electron shells, to illustrate how covalent bonds are formed. The diagrams below illustrate the formation of a single and a double covalent bond.

Covalent Compounds – Properties

    • Covalent bonding forms simple covalent compounds, or giant covalent compounds.
      • Simple covalent compounds are called molecules. 
  • Molecular structures

        • Are usually gasses (such as oxygen and ammonia molecules) or liquids (such as water and cooking oil) under normal conditions of temperature and pressure.
        • have low melting and boiling points, because although they have strong intramolecular forces of attraction (covalent bonds), they have weak intermolecular forces that hold the molecules together. So, only a small amount of energy is required to break the molecules apart during heating. 
        • lack the ability to conduct electricity in any state as they do not have any free delocalized ions or electrons, to carry an electric charge.
        • Can be polar or nonpolar.
          • Polar bond – electrons unevenly shared between atoms which have different electronegativity strength. For e.g., water.
          • Non-polar – electrons shared evenly in the bond; i.e., no difference in electronegativity. For e.g., chlorine molecule.

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