Ionisation energy

• What is the first ionisation energy

  The amount of energy required to remove 1 mol of electrons from 1 mol of atoms in a gaseous state
• Equation for first Ionisation energy

  X(g) -> X+(g) + e-
• Equation for second Ionisation energy

  X+(g) -> X2+ + e-
• Factors affecting Ionisation energy

  atomic radius

  Nuclear charge

  Electron shielding/screening
• How atomic radius influences ionisation energy

  The greater the atomic radius, the weaker the nuclear attraction is
• How Nuclear charge influences ionisation energy

  The greater the no. of protons, the greater the nuclear attraction is
• How electron sheilding influences ionisation energy

  The more inner electron shells there are, the greater the electron sheilding and the wekaer the nuclear attraction gets
• Nuclear charge

  The attraction between posotive protons and negative electrons
• Ionisation energy trend across a period


  IE increases across a period as:

  -nuclear charge increases

  -atomic radius decreases to an extent

  So, more energy is required to remove an electron
• Ionisation energy trend down a group

  IE decreases down a group as:

  • Atomic radius increases
  • there is greater electron sheilding
  • Overall there is less nuclear attraction

  So, less energy is required to remove an electron