The Periodic table and Periodicy

• First ionisation energy 


  the energy required to remove one electron from each atom in one mol of gaseous atoms of an element to form one mol of gaseous 1+ ions.
• Ionisation energy

  the energy required to remove one electron from each ion in one mol of gaseous ions.
• why do ionisation energies increase?


  For each successive ionisation energy the proton:electron ratio increases therefore these is more positive charge attracting the remaining electrons each time. every time an electron is removed the outermost electron is attracted more strongly.
• Why are there big jumps in ionisation energy 


  electrons in inner shells experience much greater attraction from the protons in the nucleus due to:

  • shorter distance between the electron and nucleus
  • less shielding from inner shells
• Factors increasing the attraction between the nucleus and electron

  • nuclear charge: how many protons in the nucleus
  • atomic radius: distance between nucleus and outermost electron
  • shielding: the more shells between the outer electron and the nucleus will shield the attraction
• trends in any group

  The first ionisation energy decreases down the group. the increased nuclear charge is outweighed by an increased atomic radius and shielding.
• Trend across a period 


  General trend is an increase in ionisation energy

  • nuclear charge - increases
  • shielding - stays the same
  • atomic radius - decreases
• periodic trend in melting points in period 2 


  • the sharp decrease in melting points marks a change from giant to simple molecular structures.
  • Li and Be are giant metallic
  • B and C are giant covalent

  
• What type of structures have a higher melting point?

  Giant structures
• Why do giant structures have a higher melting point?

  Because they have stronger forces to overcome
• What type of forces do simple molecules have to overcome?

  Weak intermolecular forces
• Why do simple molecules have lower melting points?

  Because they only have weak intermolecular forces to overcome
• periodic trends in melting points across period 3 


  • Na,Mg,Al are giant metallic
  • Si is giant covalent
  • P ,S, Cl, Ar are simple molecules

  
• what bonds/forces need to be broken in the simple molecules in period three?


  London forces