Each further removal costs more energy, with a large jump when a core electron must be removed.
Practise Atomic Structure & Periodicity All Atomic Structure & Periodicity topics
The successive ionisation energies are the energies needed to remove the second, third and later electrons, written IE2, IE3 and so on. Each further removal costs more energy, because the ion already has a higher positive charge and the remaining electrons are held more tightly. A sudden large jump occurs when the next electron must come from a stable inner shell, which is much harder to remove. The size of the jump reveals the number of valence electrons. Successive values are therefore a direct experimental probe of electron shell structure.
Key ideas: IE1 less than IE2 less than IE3, and a huge jump appears when removing a core electron. The jump tells the number of valence electrons: Mg has IE1 738, IE2 1451, IE3 7733 kJ per mol, so 2 valence electrons. Each removal leaves a smaller ion with a higher Z_eff.
Common mistakes and connections: Students expect a gradual rise and miss the jump, or think the jump comes after the first electron for all elements. For a group 13 element, the jump occurs between IE3 and IE4. Plot log IE versus electron number to see the shell structure, which is experimental evidence for shells. It connects to stable ion charges.
Magnesium shows a huge jump from IE2 to IE3 because the third electron comes from the inner shell, proving it has two valence electrons. The interactive lesson shows this as a live animation or chart.
Magnesium has an IE2 of about 1451 kJ/mol but an IE3 of about 7733 kJ/mol, a huge jump because the third electron must come from the stable inner 2p shell.
Each further removal costs more energy, with a large jump when a core electron must be removed.
Successive Ionization Energies is a intermediate topic in Atomic Structure & Periodicity. It builds on the vocabulary of beginner topics in this area.
Study these earlier topics in Atomic Structure & Periodicity first: Ionic Radius, Isoelectronic Species, Ionization Energy.
The next topics in Atomic Structure & Periodicity are Anomalies in Ionization Energy and Electron Affinity.
Yes. The interactive lesson includes a self-check question on Successive Ionization Energies, and the Atomic Structure & Periodicity quiz draws on every topic in this area.
Successive Ionization Energies is topic 87 of 115 in Atomic Structure & Periodicity.