Ionisation Energy
Use this landing page to move quickly between the key ionisation energy revision pages for Topic 1. Each card links to a focused page covering first ionisation energy, successive ionisation energy, periodic trends and group trends.
Choose an Ionisation Energy Page
Ionisation energy measures the energy required to remove an electron from a gaseous atom or ion. These pages build from the definition of first ionisation energy through to successive ionisation energy patterns and the main periodic trends across a period and down a group.
Key idea: Ionisation energy depends on nuclear charge, atomic radius, electron shielding and the subshell from which the electron is removed.
Ionisation
Introduction to Ionisation Energy
Revise the definition of first ionisation energy, state symbols and the factors that affect electron removal.
Values
Successive Ionisation Energies
Use successive ionisation energy data to identify electron shells, group number and large jumps between energy levels.
Trends
Trends in a Period
Explain why first ionisation energy generally increases across a period, including the small drops at key points.
Trends
Trends in a Group
Explain why first ionisation energy decreases down a group as shielding and atomic radius increase.
How to Use These Pages
Start with the definition of first ionisation energy so that your equations, state symbols and explanations are accurate. Then move to successive ionisation energy, because the large jumps help reveal electronic structure. Finally, use the period and group trend pages to practise explaining patterns using nuclear charge, shielding, atomic radius and subshell energy.
Exam focus: When explaining ionisation energy, always connect the trend to attraction between the nucleus and the outer electron. Use precise factors rather than vague statements about atoms being bigger or smaller.
Copyright notice: This revision page, including its written explanations, layout and teaching sequence, is produced for Online Learning System by Dr. Mohammed Al-Fatah. It is intended for student revision and may not be copied, redistributed or republished without permission.