Chemical bonds and types of bonding

• Compounds are substances in which 2 or more elements are chemically combined
• There are 3 types of strong chemical bonds: ionic, covalent and metallic
• Ionic bonding:

  • Particles are oppositely charged ions
  • Occurs in compounds formed from metals combined with non-metals
• Covalent bonding:

  • Particles are atoms which share pairs of electrons
  • Occurs in most non-metallic elements and in compounds of non-metals
• Metallic bonding:

  • Particles are atoms which share delocalised electrons
  • Occurs in metallic elements and alloys
• In ionic bonding, metal atoms lose electrons to become positively charged ions, while non-metal atoms gain electrons to become negatively charged ions
• Ions produced by metals in Groups 1 and 2 and by non-metals in Groups 6 and 7 gain a full outer shell of electrons, having the same electronic structure as a noble gas (Group 0 element)
• Ionic compounds have a giant structure of ions held together by strong electrostatic forces of attraction between oppositely charged ions
• Covalent bonding involves atoms sharing one or more pairs of electrons
• Small molecules like HCl, H2, O2, Cl2, NH3, CH4 have strong covalent bonds within their molecules
• Polymers are large covalently bonded molecules
• Giant covalent structures (macromolecules) consist of many atoms covalently bonded in a lattice structure, for example: diamond, silicon dioxide
• Metallic bonding consists of positive ions and delocalised electrons arranged in a regular pattern
• Delocalised electrons in metallic bonding are free to move through the structure, shared so metallic bonds are strong