Write electron configurations of atoms and ions up to atomic number 36 using shells and s, p and d subshells.

In the subtopic Electron configuration and ionisation energy, this AQA A-Level Chemistry 7405 learning objective focuses on write electron configurations of atoms and ions up to atomic number 36 using shells and s, p and d subshells. 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 electron configuration, shell, subshell. Electron configuration. means the arrangement of electrons in an atom’s shells and subshells, expressed using principal quantum numbers (n) and subshell labels (s, p, d, f) Avoid the mistake of students often confuse the order of filling subshells, incorrectly writing electron configurations for elements; instead, to correctly write electron configurations, follow the Aufbau principle: fill the lowest energy subshells first. For example, for atomic number 12 (Magnesium), the correct configuration is 1s² 2s² 2p⁶ 3s². This shows that the 3s subshell is filled after the 2p subshell For exam answers, practice writing electron configurations for elements up to atomic number 36, focusing on the correct order of filling s, p, and d subshells