Trends in the properties of the Period 3 elements

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  • Period 3 and its trends
    • Melting and boiling point
      • Increase from Na to Al
        • Strength of metallic bond increases
        • Charge on ion increases-more electrons join the delocalised sea and so strengthen bond
      • General decrease from semi-metals to non-metals
        • Depends on size of VDW forces and how close molecules pack together
          • The larger the VDW forces, the higher the mp and bp
        • S8 > P4 > Cl2
    • Atomic Radii
      • Dependent on the bonds being formed e.g. covalent, ionic etc.
      • Decreases across period
        • Increase in nuclear charge as protons and electrons are added as your progress from left to right
          • Increase in N.C means shells are highly attracted to nucleus and pulled further in towards it
        • No increase in electron shells so no extra shielding
          • Increase in N.C means shells are highly attracted to nucleus and pulled further in towards it
      • Taken to be half the distance between the centres of a pair of atoms
        • No point in an atom where the electron cloud drops to zero so two atoms are used
    • First Ionisation Energy
      • Energy needed to remove one mole of electrons from one mole of gaseous atoms, forming a +1 charge ion
      • Increases across a period
        • Nuclear charge increases as proton number increases across
          • Makes it harder for an electron to be removed across the period and more energy is required
      • Drop from one period to the next
        • Increase in atomic radius so attraction decreases due to an extra shell being added

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