Classification of Elements and Periodicity in Properties
Why do sodium and potassium behave alike, and why do noble gases resist reaction. This chapter in NCERT Class 11 Chemistry, Chapter 3, traces the path from early triads and Newlands octaves to Mendeleev table and the modern long form based on atomic number. It explains periods, groups, s p d and f blocks, and trends in atomic size, ionisation enthalpy, electron gain enthalpy and electronegativity. You will learn to predict chemical behaviour and reactivity from position in the periodic table.
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