Chapter 14.3, Problem 2RQ

Interpretation Introduction

Interpretation:The types of forces that hold different crystalline solids together needs to be explained.The solids that will have the lowest boiling point needs to be determined.

Concept introduction: A crystalline solid is characterized by a regular arrangement of its components. There are many types of crystalline solids such as ionic solids, molecular solids, covalent network solids, and metallic solids.

Answer to Problem 2RQ

Types of solid	Attractive force	Examples
Molecular solid	Dipole-dipole interaction, or London dispersion force or hydrogen bonding.	${\text{C}}_{\text{12}}{\text{H}}_{\text{22}}{\text{O}}_{\text{11}}$, ${\text{CCl}}_{\text{4}}$ and dry ice ( ${\text{CO}}_{\text{2}}$)
Ionic solid	Coulombic or electrostatic interaction	$\text{NaCl}$ and $\text{MgO}$
Metallic or atomic solid	Metallic bonding	Fe , Cuand Ag
Covalent or network solid	Covalent bonding	Diamond (C), graphite and quartz.

Molecular solids have the lowest melting point.

Explanation of Solution

Molecular solids are prone to melt at relatively low temperatures because the intermolecular forces that exist among the molecules are relatively weak. If the molecule is polar(possess a dipole moment) then dipole-dipole forces hold the solid together. If the molecule is non-polar,then only London dispersion forces hold the solid together.

Ionic solids are stick together by electrostatic interaction forces between the oppositely charged ions namely cation and anion arranged in a 3D lattice. Since ions are held together tightly, it takes lots of energy to break the bonds. Hence ionic solids have a high melting point.

Covalent solids have the highest melting points because it requires lots of energy for breaking of covalent bonds.

Conclusion

Types of solid	Attractive force	Examples
Molecular solids	Dipole-dipole interaction, or London dispersion force or hydrogen bonding.	${\text{C}}_{\text{12}}{\text{H}}_{\text{22}}{\text{O}}_{\text{11}}$, ${\text{CCl}}_{\text{4}}$ and dry ice ( ${\text{CO}}_{\text{2}}$)
Ionic solid	Coulombic or electrostatic interaction	$\text{NaCl}$ and $\text{MgO}$
Metallic or atomic solid	Metallic bonding	Fe , Cuand Ag
Covalent or network solid	Covalent bonding	Diamond (C), graphite and quartz.

Molecular solids have the lowest melting point.