Electron configuration and quantum numbers take centre stage in this Grade 12 Science worksheet, with a focus on how electrons occupy atomic orbitals and how their arrangement connects to chemical behaviour. Students work with the four quantum numbers, orbital-filling rules, and the chromium and copper exceptions before exploring what photoelectron spectroscopy reveals about atomic structure.

From quantum numbers to orbital diagrams

The reading passage introduces the four quantum numbers and the information each one provides: principal number (n) for the energy level, azimuthal number (l) for the subshell, magnetic number (ml) for an orbital within that subshell, and spin number (ms) for the electron's spin state. It then explains the Aufbau principle, Pauli exclusion principle, and Hund's rule, giving students a foundation for interpreting electron configurations and orbital diagrams.

Particular attention is given to two important exceptions to straightforward Aufbau predictions. Students examine the ground-state configurations of chromium, [Ar] 3d⁵ 4s¹, and copper, [Ar] 3d¹⁰ 4s¹, and consider how these arrangements relate to electronic stability. The passage also introduces photoelectron spectroscopy, including how measured electron energies and spectral peaks provide evidence about occupied subshells.

What students practise

The activities move from identifying individual rules to applying them in atomic examples. Multiple-choice questions and true-or-false statements check knowledge of quantum-number meanings, possible magnetic quantum numbers in a d subshell, electron limits within an orbital, and the correct order and pattern of orbital filling. Students also distinguish the ground-state configurations of chromium and copper and connect d subshell occupation with the periodic table's d block.

Short-answer responses ask students to explain the purpose of the four quantum numbers, account for the chromium and copper configurations, and describe how photoelectron spectroscopy can be used to investigate electron arrangements. A labeled diagram, categorizing activity, and short-note task provide additional ways to work with the topic.

Included with the worksheet

• Printable Grade 12 Science worksheet with a focused reading passage and varied practice activities.
• Student Notes lines at the bottom of the worksheet for written explanations and working.
• Separate PDF answer key for checking student responses.
• Teacher Guide within the answer key PDF, with Learning Objectives, Teaching Tips, Discussion Questions, and Common Mistakes.

Classroom use and curriculum reference

Use this electron configuration practice as a lesson companion after introducing atomic orbitals, as independent classwork, or as a review before an assessment on electronic structure. The progression from quantum-number definitions to filling rules, anomalous configurations, and spectroscopy gives students several opportunities to connect symbolic notation with the evidence scientists use to study atoms.

The resource is identified with the TEKS framework and supplied standard code SCI.12.5. Its answer key and embedded teacher guidance make it easier to check responses and prepare follow-up discussion around common difficulties with orbital filling and electron configurations.