Ionic bonding

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  • Ionic Bonding
    • Ions
      • electrons transferred from 1 atom to another
      • simplest are atoms which have lost or gained 1,2 or 3 electrons so they have a full outer shell
      • elements in same group all have same number of outer electrons
        • they lose/gain same number to get full outer shell
          • form ions with same charges
      • group 1 lose 1 electron to form 1+ ions
      • group 2 lose 2 electrons to form 2+ ions
      • group 6 elements gain 2 electrons to form 2- ions
      • group 7 elements gain 1 electron to form 1- ions
    • Ionic Compounds
      • electrostatic attraction holds positive & negative ions together - very strong
      • when atoms are held together in lattice - ionic bonding
      • oppositely charged ions come together & form ionic bonds - ionic compounds
      • e.g. sodium chloride
        • NaCl - sodium atom loses electron to form Na+ ion & each chlorine gains an electron to form Cl- ion
        • made up of Na+ ions & Cl- ions held together by electrostatic attraction in 1:1 ratio
    • Giant Ionic Lattices
      • ionic crystals are giant lattices of ions
      • 'giant' because it is made up of the same basic unit repeated over & over again
      • e.g. sodium chloride
    • Behaviour of Ionic Compounds
      • electrical conductivity
        • conduct electricity when molten/dissolved
        • ions in liquid are free to move & they carry a charge
      • melting point
        • high melting point
          • giant ionic lattices are held together by strong electrostatic forces
            • takes loads of energy to overcome these forces so melting points are very high
      • solubility
        • tend to dissolve in water
          • water molecules are polar
            • water molecules pull ions away from lattice & cause it to dissolve

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