Introduction to Chemistry Part 3 Give a description and example of the following: Covalent Bonding A covalent bond is a chemical link formed between two non-metal atoms, with similar or exact electronegativity values. They combine together by sharing electron pairs, which allow each atom to achieve a stable outer shell. They do not conduct electricity, as they do not have any ions or free electrons. An example of a covalent bond is water. It contains two hydrogen atoms, which share their single electrons with an oxygen atom. In return, the oxygen atom shares its own two electrons. It is created because of the higher electronegativity of oxygen. Figure 1: Water, H2O, BBC, 2011 This is a dot and cross diagram of water molecule. Oxygen atoms can each form two covalent bonds, whereas hydrogen atoms can each only form one. There are two pairs of electrons shared in the water molecule. Ionic Bonding An ionic bond is the transfer of valence electrons between a metallic atom to a non-metallic atom, to create two oppositely charged ions. This compound is named an ionic compound. The outer electrons on one of the atoms are transferred permanently to the other atom. The atom that loses its electrons becomes a positively charged ion, while the one that gains them becomes a negatively charged ion. Figure 2: Ionic bonding in sodium chloride, askmichellechemistry, 2012. This is an example of ionic bonding in sodium chloride. Sodium loses an electron to become a positive ion. The electron then joins the outer shell on chloride, which then becomes a negatively charged ion. Metallic Bonding Metallic bonds hold together the particles in a metal. A metallic bond results from the sharing of electrons by atoms. Van der Waals Forces Van der Waals forces are the forces that assist with intermolecular bonding between electrically neutral atoms and molecules. They are much weaker than other types of bonding. The only molecules they are powerful in are ones with no other types of intermolecular forces of attraction, such as discrete non-polar molecules and the Group 0 elements. Van der Waals’ forces are a result of electrostatic attraction between temporary dipoles and induced dipoles caused by movement of electrons in atoms and molecules.