• The?first ionisation energy (IE1)?is the energy required to?remove?one mole of electrons from one mole of atoms of an element in the?gaseous state?to form one mole of?gaseous ions
  • Eg. the first ionisation energy of Na is:

   

Na (g) → Na+?(g) + e-

IE1?Values of the Period 3 Elements

• There is a general?increase?in?IE1across a period
  • The nuclear charge?increases
  • The atomic radius?decreases
  • There are?stronger?attractive forces between the nucleus and outer electrons
  • It therefore gets harder to remove any electrons

   

• Small ‘dips’ are observed between Mg - Al and P - S