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.