Electron configuration

• Why do covalent bonds form?

  Because each atom wants to achieve a full outer shell of electrons.
• How do atoms achieve a full outer shell of electrons?


  By sharing electrons.
• Why is it difficult for covalent bonds to come apart?

  The attraction of the nuclei for the shared pair of electrons is greater than the repulsion between the positively charged nuclei.
• How do covalent bonds differ from ionic bonds?

  Covalent bonds involve sharing electrons, while ionic bonds involve transferring electrons.
• What is a covalent bond defined as?

  A shared pair of electrons.
• What is a single covalent bond?

  • Atoms are bonded by a single shared pair of electrons.
  • The attraction is localized between the shared electrons and the nuclei.
• How is a single covalent bond represented in diagrams?

  By a single line between two atoms.
• What noble gas electron configuration do the hydrogen atoms in H2 achieve?

  Helium (1s$^2$).
• What should you do for each molecule listed in the study material?

  1. Draw the dot-and-cross diagram (show outer shell electrons).
  2. Count the number of covalent bonds formed.
  3. State the number of lone pairs of electrons on any atoms.
• How many covalent bonds do the following elements form?

  • Carbon forms 4 bonds.
  • Nitrogen forms 3 bonds.
  • Oxygen forms 2 bonds.
  • Hydrogen forms 1 bond.
• How do attractions in covalent bonding differ from ionic bonding?


  Covalent bonding attractions are localized, while ionic bonding attractions act in all directions.
• What happens when two oxygen atoms form a double bond?


  • Each oxygen atom shares two electrons.
  • Each atom achieves a full outer shell (noble gas configuration of neon).
  • Two pairs of electrons are shared, forming O=O.
• What is a lone pair of electrons?

  A pair of electrons in the outer shell not involved in bonding.