Filling electron shells
Filling electron shells
Electrons occupy fixed energy levels called shells around the nucleus. For the first 202020 elements, the first shell holds up to 222 electrons, while the second and third shells hold up to 888 electrons each.
Step-by-step lessons on Edexcel GCSE Chemistry 2.2.3 Electronic configuration and position in the periodic table. Each one builds up to exam-style questions. Nail the core quantitative topics — moles, balancing equations and calculations — early on, since they underpin higher-tier questions across every paper and topic.