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Chemistry of p-Block Elements Overview

Apr 23, 2025

Unit 7: Chemistry of p-Block Elements

Overview

  • p-Block elements: Groups 13 to 18 in the periodic table.
  • Valence shell configuration: ns²np¹⁶ (except Helium with 1s²).
  • Influenced by: Atomic sizes, ionisation enthalpy, electron gain enthalpy, and electronegativity.
  • Presence of metals, metalloids, and non-metals leads to diverse chemical properties.

Unit Objectives

  • Study chemistry of elements in Groups 15, 16, 17, and 18.
  • Learn about preparation, properties, and uses of elements like dinitrogen, phosphorus, dioxygen, ozone, chlorine, etc.
  • Understand allotropic forms and compounds of sulfur.
  • Explore uses and importance of noble gases.

Group 15 Elements: Nitrogen Family

Occurrence

  • Elements: Nitrogen, Phosphorus, Arsenic, Antimony, Bismuth.
  • Trends: Shift from non-metallic to metallic character down the group.
  • Sources:
    • Nitrogen: Atmosphere (78% by volume), sodium nitrate (Chile saltpetre), potassium nitrate (Indian saltpetre).
    • Phosphorus: Found in minerals like apatite.

Properties

  • Electronic Configuration: ns²np³.
  • Ionisation Enthalpy: Decreases down the group.
  • Covalent and Ionic Radii: Increase down the group.
  • Electronegativity: Decreases down the group.
  • Oxidation States: Common ones are -3, +3, +5.

Anomalous Properties of Nitrogen

  • Small size and high electronegativity.
  • Forms multiple bonds; restricted to a maximum covalency of 4.

Reactivity

  • Hydrogen: Forms hydrides like NH₃ (ammonia).
  • Oxygen: Forms oxides E₂O₃ and E₂O₅.
  • Halogens: Forms halides EX₃ and EX₅.
  • Metals: Form binary compounds with 3 oxidation state.

Group 16 Elements: Oxygen Family

Occurrence

  • Elements: Oxygen, Sulfur, Selenium, Tellurium, Polonium.
  • Sources: Oxygen is highly abundant; sulfur found in sulfates and sulfides.

Properties

  • Electronic Configuration: ns²np⁴.
  • Oxidation States: -2, +2, +4, +6.
  • Anomalous Behaviour of Oxygen: Small size, limited covalency (<4).

Reactivity

  • Hydrogen: Forms hydrides like H₂O and H₂S.
  • Oxygen: Forms oxides EO₂ and EO₃.
  • Halogens: Forms halides like SF₆.

Group 17 Elements: Halogens

Occurrence

  • Elements: Fluorine, Chlorine, Bromine, Iodine, Astatine.
  • Sources: Found in various minerals and sea water.

Properties

  • Electronic Configuration: ns²np⁵.
  • Ionisation Enthalpy: High.
  • Electronegativity: Highest fluorine.
  • Physical State: F₂ and Cl₂ gases, Br₂ liquid, I₂ solid.

Reactivity

  • Strong oxidising agents.
  • Form interhalogens like XX₁, XX₃, XX₅, XX₇.

Group 18 Elements: Noble Gases

Occurrence

  • Elements: Helium, Neon, Argon, Krypton, Xenon, Radon.

Properties

  • Electronic Configuration: ns²np⁶ (except He: 1s²).
  • Inertness: Due to stable electronic configuration.
  • Atomic Radii: Large due to weak interatomic forces.

Reactivity

  • Least reactive, few compounds known mainly with Xenon.

Uses

  • Helium: Filling balloons, cooling superconducting magnets.
  • Neon: Lighting and displays.
  • Argon: Inert gas in metallurgical processes.

Summary

  • Covered p-block elements from Groups 15 to 18.
  • Discussed occurrence, properties, trends, and reactivity of each group.
  • Explored specific compounds and industrial processes related to these elements.