Some of the important properties of ionic compounds are as follows:
i. low electrical conductivity as solids and high conductivity in solution or when molten
ii. relatively high melting and boiling points
iii. brittleness iv. solubility in polar solvents
How does the concept of ionic bonding discussed in this chapter account for these properties?
The Correct answer and Explanation is:
Ionic compounds exhibit distinct properties that can be attributed to the nature of ionic bonding. These properties include low electrical conductivity as solids, high conductivity when dissolved in polar solvents or molten, high melting and boiling points, brittleness, and solubility in polar solvents. Understanding ionic bonding provides insight into why these properties arise.
- Low Electrical Conductivity as Solids: In ionic compounds, ions are held together by strong electrostatic forces in a crystal lattice structure. This rigid structure prevents the movement of ions, meaning that solid ionic compounds cannot conduct electricity. However, when these compounds dissolve in polar solvents (like water) or are melted, the ionic bonds are broken, allowing the ions to move freely. This mobility enables the solution or molten state to conduct electricity effectively.
- High Melting and Boiling Points: The strong electrostatic attraction between positively and negatively charged ions in ionic compounds requires significant energy to overcome. As a result, ionic compounds typically have high melting and boiling points. For example, sodium chloride (table salt) has a high melting point due to the strength of the ionic bonds that must be broken for the solid to transition to a liquid.
- Brittleness: Ionic compounds are brittle due to their crystal lattice structure. When force is applied, like-charged ions can be forced together, leading to repulsion and the breaking of the crystal. This results in the fracturing of the material rather than deforming it, which is characteristic of brittle materials.
- Solubility in Polar Solvents: Ionic compounds are often soluble in polar solvents because the polar molecules can stabilize the ions as they dissociate. Water, a polar solvent, interacts with the charged ions, effectively pulling them apart and allowing them to disperse throughout the solution.
In summary, the properties of ionic compounds arise from the strong ionic bonds between ions, their structural arrangement in a crystal lattice, and their interaction with polar solvents, all of which are fundamentally tied to the concept of ionic bonding.