Chapter 1: Periodic Classification of Elements and Periodicity

• Al-Razi: Classified elements into Metals and Non-metals.
• Dobernier's Triads (1829): Groups of 3 elements where middle one has atomic mass average of other two (e.g., Li, Na, K).
• Newlands Octaves (1864): Every 8th element repeats properties of first (like musical notes). Failed for heavier elements.
• Mendeleev's Periodic Table (1871): Arranged by increasing atomic mass. Predicted undiscovered elements (Ge).
• Modern Periodic Law (Moseley 1913): Properties are periodic function of Atomic Number.

Groups (Vertical Columns): 1-18 (IA-VIIIA). Periods (Horizontal Rows): 7.

• Short Periods: 1 (2 elements), 2 & 3 (8 elements).
• Long Periods: 4 & 5 (18 elements), 6 (32 elements), 7 (Incomplete/32).
• Blocks: s-block (IA, IIA), p-block (IIIA-VIII A), d-block (Transition Metals), f-block (Lanthanides/Actinides).

• Atomic Radius: Decreases along period (effective nuclear charge increases). Increases down group (shells added).
• Ionic Radius: Cation < Neutral Atom. Anion > Neutral Atom.
• Ionization Energy (I.E): Energy to remove electron. Increases along period (size decreases). Decreases down group (shielding effect).
• Electron Affinity (E.A): Energy released when adding electron. Increases along period. Decreases down group.
• Metallic Character: Increases down group. Decreases along period.
• Melting/Boiling Points:
  • Groups IA-IVA: Increase up to Group IV (max binding electrons).
  • Groups VA-VIIIA: Decrease (weak intermolecular forces).
• Hydration Energy: Depends on charge/size ratio. Increases with charge and decreasing size (e.g., Al³⁺ > Mg²⁺ > Na⁺).

Binary compounds with Halogens.

• Ionic Halides: Group IA, IIA. High MP/BP. Conduct in molten state. Fluorides > Chlorides > Bromides > Iodides.
• Covalent Halides: Non-metals. Low MP/BP. Volatile.
• Polymeric Halides: Intermediate (e.g., AlCl3, SiCl4). Chains/Layers.
• Trend: Ionic character decreases from Left to Right (NaCl > MgCl2 > AlCl3 > SiCl4).

Binary compounds with Hydrogen.

• Ionic (Saline) Hydrides: Group IA, IIA (s-block). Solid, high MP. Conduct electricity in molten state. H⁻ ion bonded to metal.
• Covalent (Molecular) Hydrides: p-block elements (III-VIIA). Gases/Volatile liquids. Low MP. Bond stability increases L->R.
• Intermediate: Be, Mg, Zn, Cd. Polymeric structure.

Binary compounds with Oxygen.

• Basic Oxides: Metals (Na2O, MgO). Form bases with water.
• Acidic Oxides: Non-metals (SO2, P2O5, Cl2O7). Form acids with water. Acidity increases L->R.
• Amphoteric Oxides: React with both acids and bases (e.g., Al2O3, ZnO, BeO).

Placed at top of Group IA but resembles:

• Group IA (Alkali Metals): 1 valence electron, forms H⁺, combines with halogens. Difference: H is non-metal, gas.
• Group IVA (Carbon Family): Half-filled shell, forms covalent bonds, reducing agent.
• Group VIIA (Halogens): Needs 1 electron to complete shell, forms H⁻ (Hydride), diatomic gas (H2).