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Types of Solids and Their Properties

Jun 5, 2025

Identifying Different Types of Solids

Ionic Solids

  • Composition: Typically made of metals + non-metals, forming ions.
    • Example: Sodium Chloride (NaCl)
  • Exceptions: Compounds like Ammonium Chloride (no metals but ionic structure).
  • Properties:
    • High melting points (e.g., NaCl = 646°C, MgO = 2852°C).
    • High lattice energy correlates with high melting points.
    • Lattice energy increases with higher ionic charges, decreases with larger atomic radii.

Molecular Solids

  • Composition: Non-metals forming molecules.
    • Examples: Carbon Dioxide (CO2), Fluorine (F2), Chlorine (Cl2).
  • Properties:
    • Generally low melting points (e.g., CO2 = -56°C, Water = 0°C).
    • Melting point increases down a group in the periodic table due to greater molecular weight and dispersion forces.
    • Varying physical states at room temperature (e.g., F2 is a gas, I2 is a solid).

Atomic Solids

  • Categories:
    1. Group 8A (Noble Gases): Low melting points, increase down the group (e.g., Neon = -249°C).
    2. Metallic Solids: Very variable melting points (e.g., Tungsten = 3422°C, Mercury = -38.8°C).
    3. Network Covalent Solids: High melting points due to strong covalent bonds (e.g., Diamond >3000°C).

Group 8A Atomic Solids

  • Examples: Neon, Argon, Krypton.
  • Trend: Melting points increase down the group.

Metallic Solids

  • Properties:
    • Conduct electricity and heat well.
    • Malleable and ductile.
  • Examples and Melting Points:
    • Zinc = 420°C, Gallium = 30°C, Mercury = -38.8°C.

Network Covalent Solids

  • Carbon Allotropes: Diamond and Graphite.
    • Diamond: Hard, excellent thermal conductor, insulator.
    • Graphite: Conducts electricity.
  • Other Examples: Silicon Carbide (SiC), Silicon Dioxide (SiO2), Boron Nitride.
    • High melting points (e.g., SiC = 2800°C).

Identifying Network Covalent Solids

  • Look for elements near metalloids: Carbon, Silicon, Boron, Nitrogen.
  • Group 3-5 elements likely form network covalent solids.

Practice Problems Summary

  1. Ionic Solid Identification:
    • Calcium Chloride (CaCl2) is ionic (composed of Ca2+ and Cl- ions).
  2. Ductility:
    • Copper is ductile (can be drawn into wires).
  3. Conductivity in Molten State:
    • Sodium Bromide (NaBr) conducts electricity when molten.
  4. Lowest Melting Point:
    • Neon has the lowest melting point compared to other types of solids.
  5. Non-Conductive Substance:
    • Diamond does not conduct electricity.

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