What are Ionic crystals?
The units have positively and negatively charged ions called Ionic crystals.
The units having lattice points are positive and negative ions. For example, in sodium chloride, the units are Na+ ions and Cl- ions. Coulombic forces of attraction hold each ion of a given sign to all ions of the opposite sign. The coulombic forces are very strong; therefore, the required energy is very high to separate ions from one another.
There are the following characteristics of ionic crystals:
- The heat of vaporization is high in Ionic crystals.
- At ordinary temperature vapour of ionic crystals is low.
- Ionic crystals have high melting and boiling point.
- Ionic crystals are hard and brittle.
- Th the solid-state ionic crystals are insulators. The reason is that ions are entrapped in fixed places in the crystal lattice and cannot move when an electric field is applied. When ionic crystal crystals are melted, they become good conductors of electricity. In the molten state, the well-ordered arrangement of ions in the crystals is destroyed, and the ion is positioned to move in the liquid medium when an electric field is applied.
- Ionic crystals are soluble in water and also in other polar solvents. Insoluble or very slightly soluble in non-polar solvents like benzene and carbon tetrachloride.
- Ionic solids are good conductors when dissolved in water. The ions held by coulombic forces fall away from one another when dissolved in water or any other solvent having a high dielectric constant. Coulomb’s law states that forces of attraction between oppositely charged particles vary inversely as the dielectric constant.
