Ionisation energies
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 3 practice questions, 4 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- How hard is it to pull an electron away?
- First ionisation energy
Read the transcript of the teaching part
Last time
Before we start: last time, in Electronic configuration, orbitals and atomic radius, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
How hard is it to pull an electron away?
Sodium gives up an electron almost eagerly, and so does potassium. Neon holds onto its electrons fiercely. The energy needed to strip an electron from an atom is a measurable number. Plotted for each element in turn, those numbers reveal the shell structure of the atom directly.
First ionisation energy
The first ionisation energy is the energy required to remove one electron from each atom in one mole of gaseous atoms, to form one mole of gaseous one plus ions. As an equation: X gas goes to X plus gas, plus an electron. State symbols matter. The units are kilojoules per mole. It is always endothermic, since energy must be put in. Sulfur: S gas goes to S plus gas, plus an electron.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: First ionisation energy · Successive ionisation energies.
The whole chapter: Atomic Structure, Atomic Structure.
Chapter 1: Atomic structure
- Protons, neutrons, electrons and isotopes 6 min
- Electronic configuration, orbitals and atomic radius 6 min
- Ionisation energies 7 min
Also for A Level Chemistry 9701
Which topics come up most in A Level Chemistry 9701 past papers, counted from every paper since 2004: Paper 2 topic frequency, Paper 4 topic frequency.