Question

1. compare the conductivity for ionic and covalent compounds. (p. 2)

Explanation:

To compare the conductivity of ionic and covalent compounds, we analyze their structures and the presence of charge carriers:

Ionic Compounds:

• Structure: Composed of ions (cations and anions) held together by strong ionic bonds in a crystal lattice (solid state).
• Conductivity in Solid State: In the solid state, the ions are locked in place within the lattice and cannot move freely. Thus, solid ionic compounds are poor conductors of electricity.
• Conductivity in Molten or Aqueous State:
• When molten (melted), the ionic bonds are broken, and the ions become mobile. These mobile ions can carry electric charge, so molten ionic compounds are good conductors.
• When dissolved in water (aqueous solution), the water molecules separate the ions (hydration), making them mobile. Aqueous solutions of ionic compounds (electrolytes) are excellent conductors.

Covalent Compounds:

• Structure: Formed by the sharing of electrons between atoms, resulting in molecules. Most covalent compounds do not dissociate into ions (except for some polar covalent compounds like acids in water).
• Conductivity in Solid, Liquid, or Gaseous State:
• In general, covalent compounds (e.g., sugar, methane, ethanol) do not have free ions or delocalized electrons to carry charge. So, they are poor conductors in all states (solid, liquid, gas) unless they react with water to form ions (e.g., HCl in water dissociates into \( \text{H}^+ \) and \( \text{Cl}^- \) ions, making the solution conductive).
• Exceptions: Some covalent compounds with delocalized electrons (like graphite, a form of carbon) can conduct electricity due to mobile electrons, but this is rare among typical covalent compounds.

Answer:

• Ionic Compounds: Conduct electricity when molten or in aqueous solution (due to mobile ions) but are poor conductors in the solid state (ions are immobile in the lattice).
• Covalent Compounds: Generally poor conductors of electricity in all states (solid, liquid, gas) unless they dissociate into ions in water (e.g., strong acids like HCl in aqueous solution).