Modern Periodic Law and Modern Periodic Table

Anand Classes presents a comprehensive explanation of the Modern Periodic Table, authored by Neeraj Anand and published by Anand Technical Publishers. This detailed guide is tailored for students preparing for JEE, NEET, and Class 11 CBSE Chemistry, covering the fundamental concepts of the Modern Periodic Law, the structure of the periodic table, and the classification of elements into periods, groups, and blocks. With a focus on clarity, exam relevance, and NCERT alignment, this article serves as an essential resource for mastering one of the most important topics in inorganic chemistry.

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Introduction to Modern Periodic Law

The Modern Periodic Law is an advanced concept that evolved from the limitations of Mendeleev’s periodic law. It was formulated after the work of Henry Moseley, who demonstrated a more fundamental property for the classification of elements — the atomic number.

Moseley’s Experiment and Observation

Henry Moseley conducted an experiment involving high-velocity electrons directed at metallic targets. He observed:

The square root of the frequency (ν) of X-rays emitted is proportional to the atomic number (Z) of the element.

This relationship is mathematically represented as:

Where:

= Frequency of X-ray
Z = Atomic Number (Nuclear Charge)
a and b = Constants

The plot of versus Z gave a straight line, indicating atomic number is a more fundamental property than atomic mass.