Which of the following is not correct for ionic crystals

Options

A. They posses high mp and bp
B. All are electrolyte
C. Exhibit the property of isomorphism
D. Exhibit directional properties of the bond

Answer

To determine which statement is not correct for ionic crystals, we need to analyze the properties of ionic crystals based on the information provided.

### Step-by-Step Solution:

1. **Identify the Constituent Particles**:
Ionic crystals are made up of ions. These ions are charged particles that result from the transfer of electrons between atoms.

**Hint**: Remember that ionic crystals consist of positively and negatively charged ions.

2. **Understand the Forces of Attraction**:
The force of attraction between the ions in ionic crystals is primarily electrostatic. This strong attraction contributes to the stability of the crystal structure.

**Hint**: Think about how opposite charges attract and how this affects the structure of ionic compounds.

3. **Melting and Boiling Points**:
Ionic crystals typically have high melting and boiling points due to the strong electrostatic forces holding the ions together.

**Hint**: Consider why stronger bonds would require more energy to break.

4. **Long Range Order**:
Ionic crystals exhibit long-range order, meaning the arrangement of ions is regular and repetitive in three dimensions.

**Hint**: Visualize the repeating patterns in a crystal lattice.

5. **Electrical Conductivity**:
Ionic crystals can conduct electricity when they are dissolved in water or melted because the ions are free to move.

**Hint**: Recall the conditions under which ionic compounds can conduct electricity.

6. **Isomorphism**:
Ionic crystals can exhibit isomorphism, which means that different compounds can crystallize in the same structure if they have similar sizes and chemical formulas.

**Hint**: Think about how similar-sized ions can fit into the same lattice structure.

7. **Anisotropic Nature**:
Ionic crystals are generally anisotropic, meaning their physical properties can vary depending on the direction in which they are measured.

**Hint**: Consider how the arrangement of ions might affect properties like conductivity or refractive index in different directions.

8. **Directional Properties of Bonds**:
The statement that ionic crystals exhibit directional properties of the bond is incorrect. Ionic bonds are not directional like covalent bonds; they are based on the electrostatic attraction between ions.

**Hint**: Remember that ionic bonds are formed by attraction between charged particles rather than sharing of electrons.

### Conclusion:
The statement that is not correct for ionic crystals is that they "exhibit directional properties of the bond." Therefore, the correct option is option 4.