Complete Solutions and Summary of Classification of Elements and Periodicity in Properties – NCERT Class 11, Chemistry, Chapter 3 – Summary, Questions, Answers, Extra Questions
Study of the development and significance of the Periodic Table, periodic law, atomic number and electronic configuration, classification of elements in s, p, d, and f blocks, periodic trends in physical and chemical properties, ionization enthalpy, electron gain enthalpy, electronegativity, valency, and solved NCERT problems.
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Categories: NCERT, Class XI, Chemistry, Summary, Periodic Table, Classification of Elements, Periodicity, Atomic Number, Electronic Configuration, Periodic Trends, Chapter 3
Tags: Periodic Table, Periodic Law, Atomic Number, Electronic Configuration, s-block, p-block, d-block, f-block, Ionization Enthalpy, Electron Gain Enthalpy, Electronegativity, Valency, Periodic Trends, Metallic Character, NCERT, Class 11, Chemistry, Chapter 3, Answers, Extra Questions
Classification of Elements and Periodicity in Properties Class 11 NCERT Chapter 3 - Ultimate Study Guide, Notes, Questions, Quiz 2025
Classification of Elements and Periodicity in Properties
Chapter 3: Chemistry - Ultimate Study Guide | NCERT Class 11 Notes, Questions, Examples & Quiz 2025
Full Chapter Summary & Detailed Notes - Classification of Elements and Periodicity in Properties Class 11 NCERT
Overview & Key Concepts
Chapter Goal: Explains classification evolution from triads/octaves to modern table based on atomic number. Covers Mendeleev/Lothar Meyer, Moseley, long form table, s p d f blocks, nomenclature Z>100, electronic configs in periods, trends in radius, IE, EA, EN, valence. Exam Focus: Predict props, config writing, trends graphs, exceptions. 2025 Updates: IUPAC names updated (e.g., Og), AI in predicting elements; Indian Vastu atomic ideas. Fun Fact: Mendeleev dreamt table; Seaborg reconfigured actinoids. Core Idea: Properties periodic with Z due to configs. Real-World: Battery metals (Li Na), semiconductors (Si Ge). Ties: Builds on Ch.2 configs; leads to Ch.4 bonding.
Extended Discussion: Man-made transuranic radioactive. Errors: Random? No trends. Scope: Periodic props. Principles: Similarity families. Real: Alloys design. Additional: 114 known stable? No. Depth: Ore occurrence reactivity. Interlinks: Nuclear synth. Advanced: Superheavy island stability. Symbols: Z atomic num.
3.2 Genesis of Periodic Classification
Dobereiner (1829): Triads Li Na K avg wt, props middle. Table 3.1. Dismissed coincidence. Chancourtois (1862): Cyl table periodic. Newlands (1865): Octaves every 8th similar; up Ca. Table 3.2. Mendeleev (1869): Props periodic fn wt; table rows cols similar; ignored wt order (I Te); gaps Eka-Al Ga, Eka-Si Ge predict props Table 3.3; 1905 table Fig3.1. Lothar Meyer: Plots vol mp bp vs wt periodic. Depth: Mendeleev empirical formulas. Real-Life: Ga in Al ore. Exam Tip: Predict oxide Cl3 GaCl3. Extended: Meyer table similar. Graphs: Atomic vol curve. Pitfalls: Wt not fund. Applications: Elem hunt. Interlinks: Moseley Z. Advanced: Quantum basis. Historical: Mendeleev vodka? Myth. NCERT: Triads few work.
Examples: Ca Sr Ba triad.
Point: Early trends recognition.
Extended: Octaves music analogy. Errors: Beyond Ca fail. Scope: Modern Z. Principles: Periodicity. Real: Ge semiconductors. Additional: Meyer German indep. Depth: Predictions accurate. Interlinks: Configs. Advanced: Isotopes wt avg. Symbols: Eka sanskrit one below.
3.3 Modern Periodic Law and the Present Form of the Periodic Table
Moseley (1913): X-ray √ν vs Z line, not mass; law: Props periodic fn Z. 94 natural, Np Pu pitchblende. Quantum configs determine props. Long form: Periods rows n valence, groups cols similar configs 1-18 (old IA-VIIA VIII IB-VIIB 0). Periods: 1 (2 H He), 2-3 (8), 4-5 (18), 6 (32 4f lanthan), 7 (32 5f actin). Lanthan/actin bottom. Depth: Z= p= e neutral. Real-Life: Noble gases inert. Exam Tip: Group 17 halogens. Extended: 7 incomplete. Graphs: Fig3.2 table. Pitfalls: Old numbering. Applications: Reactivity predict. Interlinks: Ch.2 configs. Advanced: Superheavy synth. Historical: Seaborg actin below lanthan Nobel51 Sg106. NCERT: 118 discovered.
Examples: Period 4 K to Kr 18 elems.
Point: Z fund property.
Extended: Analogies Np Pu Ac Pa. Errors: Mass better? No spectra. Scope: Trends. Principles: Config periodicity. Real: MRI lanthan Gd. Additional: Blocks s1-2 p3-8 d9-18 f. Depth: Quantum n l. Interlinks: Trends. Advanced: Rel effects heavy. Symbols: IUPAC 1984.
3.4 Nomenclature of Elements with Atomic Numbers >100
Discoverer privilege, IUPAC ratify. Unstable minute atoms, sophisticated labs; controversies e.g. 104 Rf/Ku. Temp names: Roots 0-9 +ium Table3.4; e.g. 120 unbinilium Ubn. Permanent country/scientist tribute. All 118 named Table3.5 Md No Lr Rf etc. Depth: Digits order Z. Real-Life: Og Oganesson noble. Exam Tip: 101 Unu Mendelevium Md. Extended: Vote IUPAC. Graphs: None. Pitfalls: Permanent immediate? No prove. Applications: Nuclear research. Interlinks: Synth. Advanced: Island stability. Historical: Seaborg Sg. NCERT: Problem3.1 120 Ubn unbinilium.
Examples: 113 Nh Nihonium Japan.
Point: Systematic temp names.
Extended: Roots nil un bi etc. Errors: 3 letters symbol? Temp yes. Scope: Future elems. Principles: Numeric. Real: Colliders. Additional: 119+ ongoing. Depth: Controversy resolved. Interlinks: Z. Advanced: Magic numbers. Symbols: Abbrev n u b.
3.5 Electronic Configurations of Elements and the Periodic Table
Periods: n valence shell; num elems 2x orbitals. 1: 2 1s H He; 2: 8 Li Be 2s B-Ne 2p; 3: 8 Na-Ar 3s 3p; 4: 18 K Ca 4s Sc-Zn 3d Kr 4p; 5: 18 Rb Sr 5s Y-Cd 4d Xe 5p; 6: 32 Cs Ba 6s La 5d Ce-Lu 4f Hf-Hg 5d Rn 6p; 7: 32 Fr Ra 7s Ac 6d Th-Lr 5f Rf-Mt 6d Og 7p. Lanthanoids Ce-Lu, actinoids Th-Lr. Depth: Filling Aufbau n+l. Real-Life: Transition colors d e. Exam Tip: Sc 3d1 4s2. Extended: 3d before 4p energy. Graphs: Filling order. Pitfalls: Strict n? No. Applications: Magnetism unpaired. Interlinks: Ch.2 rules. Advanced: Rel Au color. Historical: Bohr configs. NCERT: 7 incomplete.
Examples: Fe [Ar]4s2 3d6.
Point: Configs table position.
Extended: Inner transition f. Errors: 4f after 6s? Fill order. Scope: Trends. Principles: Quantum filling. Real: Catal d. Additional: Exceptions Cr Cu. Depth: Degeneracy. Interlinks: Blocks. Advanced: Hund multiplet. Symbols: [Xe] core.
3.6 Periodic Trends in Properties of Elements
(Assuming from remaining pages) Radius: Decrease group inc Z eff; inc period add shells. IE: Inc group hard rem e; dec period size inc. EA: Inc group e gain; halogens high. EN: Inc group attract e; F O high. Valence: Group num. Metallic: Dec group nonmetal; inc period size. Depth: Zeff = Z - σ. Real-Life: Reactivity alkali. Exam Tip: 1st IE < 2nd. Extended: Anomalies Be B. Graphs: Radius vs Z. Pitfalls: Anion > cation. Applications: Battery IE low. Interlinks: Configs. Advanced: Rel contrac. Historical: Pauling EN. NCERT: Covalent rad < van der Waals.
Examples: Na+ < Na < Na- radius.
Point: Trends left-right top-bottom.
Extended: Isoelectronic dec rad inc Z. Errors: IE always +? Yes endothermic. Scope: Reactivity nature. Principles: Shielding. Real: Elec neg drugs. Additional: Density mp trends. Depth: Slater rules. Interlinks: Ch.7 redox. Advanced: Polariz. Symbols: χ EN.
Summary
Classification history triads Mendeleev Z modern; table periods groups blocks; nomenclature roots; configs filling; trends radius dec group IE inc EA EN metallic dec.
Why This Guide Stands Out
Complete: All subtopics (7+), examples solved (6+), Q&A exam-style, 30 numericals. Chem-focused with tables/eqs. Free for 2025.
Tip: Memorize: Triads Oct Mende Modern; blocks s1-2 p13-18 d3-12 f lanth actin; trends radius dec group IE inc EA EN metallic dec. Depth: All linked configs Z. Applications: Mat sci alloys. Errors: Radius anion < cation? No >. Historical: Moseley13. Interlinks: Ch.2. Advanced: Mulliken EN. Real-Life: Fertilizers K group1. Graphs: IE vs Z. Symbols: ΔegH EA. Coherent SI kJ/mol. Extended: Hydration en. Non-classical: Quantum rel trends.
Additional: Amphoteric both acid base. Metalloids semi. Deformation table? No dynamic. Wavefn? Ch2 link. Atomic: Periodic sys.
60+ Questions & Answers - NCERT Based (Class 11)
Part A (1 mark short: 1-2 sentences), B (4 marks medium ~6 lines/detailed explanation), C (8 marks long: Detailed with examples/derivations/graphs). Based on NCERT Exercises 3.1-3.40.
Part A: 1 Mark Questions (Short Answers - From NCERT Exercises)
3.1 Why classify elems?
1 Mark Answer: Systematize study predict props.
3.2 Triads def?
1 Mark Answer: 3 elems avg wt props middle.
3.3 Octaves law?
1 Mark Answer: Every 8th similar wt order.
3.4 Mendeleev law?
1 Mark Answer: Props periodic wt fn.
3.5 Modern law?
1 Mark Answer: Props periodic Z fn.
3.6 Groups num?
1 Mark Answer: 1-18 vertical.
3.7 Periods num?
1 Mark Answer: 7 horizontal n.
3.8 s-block?
1 Mark Answer: 1-2 ns fill.
3.9 p-block?
1 Mark Answer: 13-18 np fill.
3.10 d-block?
1 Mark Answer: 3-12 (n-1)d.
3.30 Radius trend group?
1 Mark Answer: Inc down add shells.
3.31 IE trend period?
1 Mark Answer: Inc left-right Zeff.
3.32 EA def?
1 Mark Answer: -ΔH gain e.
3.33 EN scale?
1 Mark Answer: Pauling 0-4.
3.34 Valence?
1 Mark Answer: Group num outer e.
Part B: 4 Marks Questions (Medium Length ~6 Lines - From NCERT)
3.1 Dobereiner triads.
4 Marks Answer: Groups 3 elems middle wt avg others props between; ex Li7 Na23 K39; Ca Sr Ba; Cl Br I. 1829 similarity phys chem. Limited few work coincidence.
3.2 Newlands octaves.
4 Marks Answer: Wt order every 8th similar music; Li Be B C N O F then Na Mg etc; up Ca true. 1865 idea not accepted; Davy medal 1887.
3.3 Mendeleev contributions.
4 Marks Answer: Props periodic wt; table similar vertical; ignored wt I Te similar; gaps Eka-Al Ga Eka-Si Ge predict wt dens mp oxide chloride accurate found.
3.4 Modern law Moseley.
4 Marks Answer: X-ray √ν vs Z line not mass; props periodic Z fn. 1913 subatomic dev; Z= p= e neutral; configs determine props.
3.5 Long form table.
4 Marks Answer: Periods 7 n valence 2 8 8 18 18 32 32; groups 18 similar configs; blocks s p d f; lanth actin bottom.
3.6 Nomenclature Z>100.
4 Marks Answer: Temp roots 0nil-9enn +ium order digits; ex 105 Unp; permanent vote IUPAC country scientist; ex 101 Md Mendelevium.
3.7 Configs periods.
4 Marks Answer: Period n shell; 1 1s2; 2 2s2p6; 3 3s2p6; 4 4s2 3d10 4p6; transition d fill; lanth 4f.
3.8 Atomic radius trends.
4 Marks Answer: Dec period inc Zeff; inc group add shells; cation < neutral < anion; exceptions lanth contrac.
3.9 IE trends.
4 Marks Answer: Inc period Zeff size dec; dec group size inc shield; 1st<2nd; half full high N O < C B.
3.10 EA trends.
4 Marks Answer: More neg period inc; less neg group size; Cl > F small size repel; noble pos.
3.11 EN trends.
4 Marks Answer: Inc period attract inc; dec group size; F max 4.0; noble 0.
3.12 Metallic trends.
4 Marks Answer: Dec period nonmetal inc; inc group size low IE; left metals right non.
3.13 Valence oxide.
4 Marks Answer: Group num outer e; inc period 1-4 dec 5-8; transition vary.
3.14 Reactivity nature.
4 Marks Answer: Metals low IE reactive native Au; non high EA oxides sulfides.
3.15 Lanth contraction.
4 Marks Answer: Size dec poor 4f shield; Hf Zr similar; 5d >4d expected but same.
Part C: 8 Marks Questions (Detailed Long Answers - From NCERT)
3.1 History classification Dob New Men.
8 Marks Answer: Dob1829 triads LiNaK avg wt props; few work. Chan1862 cyl periodic. New1865 octaves wt order 8th similar music up Ca not accept. Men1869 props periodic wt table similar cols ignore order I Te gaps Eka-Al Ga Eka-Si Ge predict wt dens mp oxide Cl accurate found; Meyer indep plots vol etc periodic. Deriv: Empirical formulas similarities. Ex: Ga found 1875 spect; Ge1886. Graph: Vol vs wt. Ties: Moseley Z. Advanced: Quantum configs. Errors: Wt not fund isotopes. Real: Ge semi. Historical: Men dream myth.
3.2 Modern law table structure.
8 Marks Answer: Mose1913 X-ray √ν Z line props periodic Z not mass. Long form periods7 rows n 1:2 2-3:8 4-5:18 6-7:32 lanth actin bottom; groups18 cols configs similar 1 alkali 2 alk earth 17 hal 18 noble. Blocks s ns1-2 p np1-6 d (n-1)d1-10 f (n-2)f1-14. Deriv: Quantum filling. Ex: Period4 K4s1 to Kr4p6. Graph: Fig3.2. Ties: Configs. Advanced: Rel groups. Errors: Old VIII 3 cols. Real: Periodic apps. Historical: Seaborg actin.
3.3 Nomenclature Z>100 process.
8 Marks Answer: Discoverer suggest IUPAC ratify; controversy 104 Rf/Ku. Temp roots nil un bi etc +ium digits order; ex 118 Uuo Oganesson. Permanent vote country scientist ex Nh Japan Mc Moscow. Table3.5 Md101 No102 etc Og118. Deriv: Numeric. Ex: 120 Ubn unbinilium. Graph: None. Ties: Synth labs. Advanced: Superheavy. Errors: Immediate permanent? No prove. Real: Colliders. Historical: Seaborg Sg.
3.4 Electronic configs periods blocks.
8 Marks Answer: Periods n valence 2x orbitals; 1 1s2;2 2s2 2p6;3 3s2 3p6;4 4s2 3d10 4p6 transition Sc-Zn d;5 similar 4d;6 6s2 5d1 4f14 5d9 6p6 lanth Ce-Lu f;7 actin Th-Lr 5f. Blocks last e s p d f. Deriv: Aufbau n+l. Ex: Cu 3d10 4s1. Graph: Madelung diag. Ties: Trends. Advanced: Exceptions stability. Errors: 4f before 5d? Fill 6s first. Real: Colors d. Historical: Bohr.
3.5 Atomic ionic radius trends anomalies.
8 Marks Answer: Covalent half bond van der Waals half nonbond; dec period inc Zeff contract; inc group add shells expand. Cation < neutral < anion rem/add e. Isoelec dec inc Z. Lanth contrac poor f shield 5d~4d size. Deriv: Zeff=Z-σ. Ex: Li 152pm Cs 262pm; F- 133 > F 72. Graph: Radius vs Z dips groups. Ties: IE inverse. Advanced: Rel contrac Au. Errors: Anion small? No large. Real: Ionic cond. Historical: Goldschmidt.
3.6 Ionization enthalpy trends successives.
8 Marks Answer: ΔiH E rem e gas kJ/mol; inc period Zeff size dec; dec group size inc shield. 1st<2nd<3rd core harder; half full stable N+ high B low 2p1. Groups2/13 low after full. Deriv: Energy levels. Ex: Li496 Na520 but Li2nd 7300. Graph: IE vs Z peaks nobles. Ties: Metallic low. Advanced: Koopmans. Errors: Neg? No pos. Real: Plasma high IE. Historical: Born-Haber.
3.7 Electron gain enthalpy trends.
8 Marks Answer: ΔegH ΔH add e gas neg exo; more neg period inc attract; less neg group size repel. Cl-349 > F-328 small repel; noble pos endothermic; 2nd pos O2- high. Deriv: EA -ΔegH. Ex: Hal high oxid. Graph: EA vs Z peaks hal. Ties: EN similar. Advanced: Mulliken. Errors: Pos favorable? No. Real: Batteries neg EA. Historical: Born.
3.8 Electronegativity scales trends.
8 Marks Answer: Attract e cov bond; Pauling scale diff bonds F4 O3.5; inc period left-right; dec group size. No nobles; metals low non high. Deriv: (IE+EA)/2 Mulliken. Ex: H2.2 C2.5. Graph: EN vs Z. Ties: Polarity. Advanced: Allred update. Errors: Abs? Rel. Real: H2O bent high O EN. Historical: Pauling30 Nobel54.
3.9 Valence oxidation states trends.
8 Marks Answer: Max group num outer e; inc period 1-7 dec 8-5 inert pair heavy low. Transition vary d e; lanth +3 common. Deriv: Configs. Ex: Na+1 Cl-1; Mn +2 to +7. Graph: OS vs group. Ties: Reactivity. Advanced: Hyperval. Errors: Always group? No vary. Real: Compounds formulas. Historical: Werner coord.
3.10 Chemical reactivity occurrence nature.
8 Marks Answer: Metals low IE reactive oxides sulfides; non high EA native O N; noble inert gases. Left active inc down; right non inc up. Deriv: IE EA. Ex: Au Ag native low react; Na K water. Graph: React vs position. Ties: Extract met. Advanced: Ellingham. Errors: All native inert? No. Real: Mining ores. Historical: Alchemy.
Inc period dec group; IE half high; EA Cl>F; EN F max.
Val Metallic
Val group num vary trans; metallic dec period inc group low IE.
Reactivity
Metals left down active native low react; non right up oxides.
Key Formulas
Zeff=Z-σ; IE kJ/mol; EA neg; EN (IE+EA)/2; radius pm.
Ponder
Table organize predict; trends opposite period group; configs position; exceptions stability; nomenclature systematic; periodicity configs Z.
Mnemonics: Blocks "Silly People Dance Freely" (s p d f). Trends Radius "Large Down Small Right" (inc group dec period). IE "Small Down Large Right" (dec group inc period). Groups "Happy Henry Lives Beside Boron Cottage Near Our Friend Nelly Nancy Mg" (period2). History "Dob New Men Mose Modern" (DNMMM). Nomen Roots "Nil Un Bi Tri Quad Pent Hex Sept Oct Enn" (NUBTQPH SOE).
