Physics

• Compounds


  Substances in which 2 or more elements are chemically combined
• Types of strong chemical bonds

  • Ionic
  • Covalent
• 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
• Formation of ionic bond


  1. Metal atom loses electrons to become positively charged ion

  2. Non-metal atom gains electrons to become negatively charged ion
• An ion is an atom that has lost or gained electron(s)
• Electron transfer during ionic compound formation


  • Dot and cross diagram (e.g. for NaCl)
• Ionic compounds


  • Giant structure of ions
  • Held together by strong electrostatic forces of attraction between oppositely charged ions
  • Forces act in every direction since the structure is in 3D
• Covalent bonding


  Atoms share one or more pairs of electrons
• Giant covalent structures (macromolecules)


  Many atoms covalently bonded in a lattice structure