Exploring Conceptual Difficulties in the Periodic Table of Elements: A Standardized Diagnostic Approach for Secondary Learners

Abstract

The Periodic Table of Elements represents a cornerstone of chemistry education, yet secondary learners frequently demonstrate persistent misconceptions and knowledge gaps in its fundamental concepts. This study sought to develop and validate a research-based diagnostic assessment tool to evaluate Grade 10 learners’ content knowledge across selected Periodic Table competencies. Employing a descriptive research design, the instrument underwent rigorous expert validation, pilot testing, readability analysis, item analysis, and standardization to ensure its reliability and suitability for classroom application. The finalized diagnostic test was administered to Grade 10 learners from selected public high schools. Findings indicated that learners’ overall content knowledge ranged from low to moderate, with none of the assessed competencies achieving full mastery. Among the competencies, determining the number of protons, neutrons, and electrons emerged as the least mastered, followed by explaining the organization of elements and periodic trends. In contrast, tracing the historical development of the Periodic Table was the most successfully demonstrated competency, suggesting that learners perform comparatively better on descriptive, recall-based tasks than on conceptual and application-oriented challenges. These results underscore enduring conceptual difficulties in atomic structure and periodic reasoning, emphasizing the need for instructional strategies that promote deep conceptual understanding and analytical thinking. The validated diagnostic assessment tool provides educators with a robust and systematic means to identify learning gaps, address misconceptions, and inform targeted instructional planning in secondary chemistry education.