Question

Which type (or types) of crystalline solid is characterized by each of the following: (a) high mobility of electrons throughout the solid; (b) softness, relatively low melting point; (c) high melting point and poor electrical conductivity; (d) network of covalent bonds; (e) charged particles throughout the solid.

Short answer

(a) Metallic solids exhibit high mobility of electrons throughout the solid. (b) Molecular solids are characterized by their softness and relatively low melting points. (c) High melting points and poor electrical conductivity are properties of ionic solids. (d) A network of covalent bonds is typical for covalent (or network) solids. (e) Charged particles throughout the solid are characteristic of ionic solids.

Step-by-step solution

(a) High mobility of electrons throughout the solid

This characteristic is typical of metallic solids. In metallic solids, the electrons are delocalized and can move freely throughout the solid. Because of this, metallic solids are excellent conductors of electricity and heat.

(b) Softness, relatively low melting point

This characteristic is typical of molecular solids. Molecular solids consist of molecules held together by weak intermolecular forces like van der Waals forces, dipoles, or hydrogen bonds. Because these forces are relatively weak, molecular solids are generally soft and have low melting points.

(c) High melting point and poor electrical conductivity

This characteristic corresponds to ionic solids. Ionic solids have high melting points because of the strong electrostatic attraction between anions and cations in their structure. These attractions give ionic solids a stable, often crystalline, structure. However, ionic solids have poor electrical conductivity because there are no mobile electrons or charged particles that can carry a charge through the solid.

(d) Network of covalent bonds

This characteristic is found in covalent (or network) solids. Covalent solids form when atoms share electrons to create a network of covalent bonds throughout the solid. This network gives covalent solids their strong and rigid structure. Common examples of covalent solids include diamond and quartz.

(e) Charged particles throughout the solid

This characteristic is typical of ionic solids. Ionic solids have a regularly repeating arrangement of charged particles (ions) held together by electrostatic forces. This repeating arrangement of charged particles gives ionic solids their crystalline structure.