Interpret ionisation energy data for Period 3 and Group 2 elements.

In the subtopic Electron configuration and ionisation energy, this AQA A-Level Chemistry 7405 learning objective focuses on interpret ionisation energy data for Period 3 and Group 2 elements. It belongs to Atomic structure, so revision should stay anchored to this exact subtopic rather than drifting into a generic GCSE-level chemistry summary. Approved keywords to use include ionisation energy, Period 3, Group 2. Ionisation energy. means the energy required to remove one mole of electrons from one mole of gaseous atoms or ions Avoid the mistake of students often think that ionisation energy increases steadily across a period and decreases down a group, ignoring the effect of subshell filling and electron shielding; instead, explain that ionisation energy rises across a period due to increasing nuclear charge and decreasing atomic radius, but drops when a new subshell begins (e.g., from Na to Mg). Down a group, ionisation energy decreases because added electrons are farther from the nucleus and more shielded, reducing the energy required to remove an electron For exam answers, when interpreting ionisation energy data for Period 3 and Group 2 elements, look for trends in the data that indicate the strength of the attraction between the nucleus and the outer electrons