Chemistry · Class 11 · Chapter 3
Classification of Elements and Periodicity in Properties
13 lessons 110 min 2 simulations
This chapter traces how chemists sorted the elements, from Dobereiner's triads and Newlands' octaves to Mendeleev's table and the modern long form built on atomic number. It then reads the table through electronic configuration (periods, groups and the s, p, d, f blocks) and explains the periodic trends in atomic and ionic size, ionization enthalpy, electron gain enthalpy, electronegativity, valence and reactivity.
What the exam asks
NEET asks for orders of size, ionization enthalpy, electron gain enthalpy and electronegativity, with the exceptions (Be > B and N > O in ionization enthalpy, Cl more negative than F in electron gain enthalpy), isoelectronic series, block and group from a configuration, IUPAC names for Z > 100 and the nature of oxides. Marks are lost by applying a trend blindly where NCERT names an exception.
Lessons
13 lessons · 110 min
1Why classify, and the first attemptsNCERT §3.1, §3.27 min2Mendeleev's periodic tableNCERT §3.27 min3Modern periodic law and the long formNCERT §3.37 min4Naming elements with Z above 100NCERT §3.46 min5Electronic configuration, periods and groupsNCERT §3.57 min6The s, p, d and f blocksNCERT §3.6.1-3.6.48 min7Metals, non-metals and metalloidsNCERT §3.6.57 min8Atomic and ionic radiiNCERT §3.7.1(a), (b)12 min 1 sim9Ionization enthalpyNCERT §3.7.1(c)11 min 1 sim10Electron gain enthalpy and electronegativityNCERT §3.7.1(d), (e)8 min11Valence and the anomalous second periodNCERT §3.7.28 min12Periodic trends and chemical reactivityNCERT §3.7.37 min13Chapter reviewMust-know facts, traps and formulas15 min