Ionisation Energy

• 1st ionisation energy

  The energy required to remove one electron from each atom in a mole of gaseous atoms producing one mole of 1+ gaseous ions
• 2nd ionisation energy

  Energy needed to remove one electron from each ion in one mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions
• Three factors that affect ionisation energy

  • Distance from the nucleus (atomic radius)
  • nuclear charge
  • Shielding
• Distance from the nucleus

  Attraction gets weaker the further from the nucleus the outer electron is

  Distance increases from one shell to the next
• Shielding

  Further down the periodic table atoms will have mor electron shells between the nucleus and outer electron

  More shells between the outer electron and nucleus the weaker the attraction due to shielding
• Down a Group (Group 2)

  Distance increases from the nucleus

  Shielding increases

  Decreasing ionisation
• Group 2 to 3 dip across a period

  • Moves from the S shell to the P shell
  • Bigger distance from the nucleus
  • More shielding
• Group 5 to 6 dip across a period

  Repulsion with the orbitals

  Electron electron repulsion when they are in the same orbital

  Leads to weaker ionisation as its easier to remove