• The?second ionisation energy?(IE2) is the energy required to remove the second mole of electrons from each +1 ion in a mole of gaseous +1 ions, to form one mole of +2 ions
• The?third ionisation energy?(IE3) is the energy required to remove the third mole of electrons from each +2 ion in a mole of gaseous +2 ions, to form one mole of +3 ions
• And so on...
• The electrons from an atom can be continued to be removed until only the?nucleus?is left
• This sequence of ionisation energies is called?successive ionisation energies

Successive Ionisation Energies of Beryllium Table

Successive ionisation energies of an element

• The?successive?ionisation energies of an element?increase
• This is because once you have removed the outer electron from an atom, you have formed a?positive ion
• Removing an electron from a positive ion is?more difficult?than from a neutral atom
• As more electrons are removed, the?attractive forces increase?due to decreasing shielding and an increase in the proton to electron ratio
• The increase in ionisation energy, however, is not constant and is dependent on the atom's electronic configuration
• Taking calcium as an example:

Ionisation Energies of Calcium Table

• The?first?electron removed has a low IE1?as it is easily removed from the atom due to the spin-pair repulsion of the electrons in the 4s orbital
• The?second?electron is more difficult to remove than the first electron as there is no?spin-pair repulsion
• The?third?electron is much more difficult to remove than the second one corresponding to the fact that the third electron is in a?principal quantum?shell which is closer to the nucleus (3p)
• Removal of the?fourth?electron is more difficult as the orbital is no longer full, and there is less?spin-pair repulsion
• The graph shows there is a large increase in successive ionisation energy as the electrons are being removed from an increasingly positive ion
• The big jumps on the graph show the change of?shell?and the small jumps are the change of?subshell

• Successive?ionisation?data?can be used to:
  • Predict or confirm the simple electronic configuration of elements
  • Confirm the number of electrons in the outer shell of an element
  • Deduce the Group an element belongs to in the Periodic Table

   

• By analyzing where the large jumps appear and the number of electrons removed when these large jumps occur, the?electron configuration?of an atom can be determined
• Na, Mg and Al will be used as examples to deduce the electronic configuration and positions of elements in the Periodic Table using their successive ionisation energies

Successive Ionisation Energies Table

Sodium

• For sodium, there is a huge?jump?from the?first?to the?second?ionisation energy, indicating that it is much easier to remove the first electron than the second
• Therefore, the first electron to be removed must be the last electron in the?valence?shell?thus Na belongs to group I
• The large jump corresponds to moving from the 3s to the full 2p subshellNa?????? 1s2?2s2?2p6?3s1

Magnesium

• There is a huge increase from the?second?to the?third?ionisation energy, indicating that it is far easier to remove the first two electrons than the third
• Therefore the?valence?shell?must contain only two electrons indicating that magnesium belongs to group II
• The large jump corresponds to moving from the 3s to the full 2p subshellMg?????? 1s2?2s2?2p6?3s2

Aluminium

• There is a huge increase from the?third?to the?fourth?ionisation energy, indicating that it is far easier to remove the first three electrons than the fourth
• The 3p electron and 3s electrons are relatively easy to remove compared with the 2p electrons which are located closer to the nucleus and experience greater?nuclear?charge
• The large jump corresponds to moving from the?third shell?to the?second shellAl???????? 1s2?2s2?2p6?3s2?3p1