Periodic Classification of Elements

NCERT Class 10 Science, Chapter 5 – Periodic Classification of Elements, from the Science Textbook, explains how scientists classified elements based on similarities in their properties. The chapter discusses early attempts of classification by Döbereiner, Newlands, and Mendeleev, which eventually led to the development of the Modern Periodic Table.


The chapter describes Döbereiner’s Triads, Newlands’ Law of Octaves, and Mendeleev’s Periodic Table. Mendeleev arranged elements according to increasing atomic masses and grouped elements with similar chemical properties together. His periodic table successfully predicted the existence and properties of several undiscovered elements, making it a major milestone in the history of chemistry.


The chapter further explains the Modern Periodic Table, which is based on increasing atomic numbers. It introduces groups and periods, electronic configuration, valency, atomic size, metallic and non-metallic properties, and periodic trends. Understanding these patterns helps students predict the behavior and properties of elements, making the study of chemistry more organized and systematic.