Covalent bonding

• How atoms can form covalent bonds


  Sharing at least one electron
• Ionic bonds

  Atoms transfer electrons from one to the other, forming oppositely charged ions that are attracted through electrostatic forces
• Atoms transfer electrons to get a full outer shell
• This works when one atom has too many electrons and the other too few, like sodium and chlorine
• When two non-metal elements like two chlorine atoms need an extra electron each, they can share electrons instead of transferring them
• Simple molecular substances


  Small molecules where atoms are joined by strong covalent bonds, but between molecules there are only weak intermolecular forces
• Giant covalent structures


  Structures like silicon dioxide, diamond, and graphite, with billions/trillions of atoms joined by covalent bonds in a regular lattice
• Atoms with full outer shells have stable electronic configurations, while those with less than eight electrons in their outer shells tend to gain or lose electrons to achieve stability.
• The number of covalent bonds an atom can form is determined by its valence shell electron configuration.
• Metals generally form positive ions (cations) as they lose electrons from their outermost energy level.
• Ionic compounds consist of positively charged metal ions and negatively charged non-metal ions held together by electrostatic attraction.
• Non-metals usually form negative ions (anions) as they gain electrons into their outermost energy level.
• A group 1 element will always form one covalent bond as it needs to lose one electron from its outermost energy level to fill its octet.
• Group 2 elements will always form two covalent bonds as they need to lose two electrons from their outermost energy level to fill their octet.
• Group 7 elements (halogens) will always form one covalent bond as they need to gain one electron from another atom to fill their octet.
• Chemical reactions involve the breaking and forming of chemical bonds.
• A reaction where existing bonds are broken is called decomposition.