Chapter 12, Problem 67A

Interpretation Introduction

Interpretation:

The types of crystalline solids that are good conductors of heat and electricity need to be determined.

Concept introduction:

Crystalline solids have repeating, 3 D patterns of molecules, atoms or ions. The particles tend to maximize the spaces occupied by them, resulting in solid formation which is incompressible.

The three main types of crystalline solids are molecular, ionic and atomic (network and metallic)

Answer to Problem 67A

• Ionic crystalline solids
• Metallic crystalline solids.

Explanation of Solution

Molecular crystalline solids are made up of molecules. These molecules have dispersion, dipole-dipole and hydrogen bonding. All these intermolecular forces are weaker than ionic bonding. Thus, molecular solids are soft and they are poor conductors of heat and electricity.

For example, ice that is solid water and dry ice that is CO₂.

Ionic crystalline solids have positive and negative ions. These ions have ion-ion attraction which is stronger than other intermolecular interactions. Thus, they are good conductors of heat and electricity.

The atomic crystalline solids contain atoms having dispersion forces. They are soft thus; they are poor conductors of heat and electricity. In network crystalline solids, atoms have covalent bonds. They are hard and have a high melting point and they are poor conductors of heat and electricity.

The metallic crystalline solids have atoms held together by metallic bonds. They are strong conductors of heat and electricity.

Thus, the crystalline solids which are good conductor of heat and electricity are:

• Ionic crystalline solids
• Metallic crystalline solids.

Conclusion

Thus, the crystalline solids which are good conductor of heat and electricity are:

• Ionic crystalline solids
• Metallic crystalline solids.