Chapter 11: Problem 56
Describe and give examples of the following types of crystals: (a) ionic crystals, (b) covalent crystals, (c) molecular crystals, (d) metallic crystals.
Short Answer
Expert verified
Ionic crystals: NaCl; Covalent crystals: diamond; Molecular crystals: I$_2$; Metallic crystals: Fe.
Step by step solution
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Ionic Crystals
Ionic crystals are a fascinating type of crystal structure where positive and negative ions come together to form an intricate lattice. This configuration gives rise to several unique properties. Because of the strong electrostatic forces that attract the oppositely charged ions towards each other, ionic crystals typically have very high melting and boiling points. This makes them quite durable in high temperature environments. However, due to their rigidity, they tend to be brittle and can fracture under pressure.
A key feature of ionic crystals is their solubility in water. When dissolved, the ions dissociate and freely move in solution, which can conduct electricity. This is why substances like sodium chloride (NaCl), which forms ionic crystals, dissolve well in water and create conductive solutions.
In summary, ionic crystals are characterized by:
A key feature of ionic crystals is their solubility in water. When dissolved, the ions dissociate and freely move in solution, which can conduct electricity. This is why substances like sodium chloride (NaCl), which forms ionic crystals, dissolve well in water and create conductive solutions.
In summary, ionic crystals are characterized by:
- High melting and boiling points
- Brittle structure
- Solubility in water
Covalent Crystals
Covalent crystals are known for their strength and durability, resulting from the firm covalent bonds that hold the atoms together in a continuous network. Because these bonds are very strong, covalent crystals often exhibit high melting points, making them resistant to changes in temperature. This bonding results in hard structures, such as diamonds, which are known for being one of the hardest natural materials.
Despite their robustness, covalent crystals generally do not conduct electricity. This is because there are no free electrons or ions to carry an electric current. Examples of covalent crystals include quartz (SiO$_2$) and diamond, both of which exemplify the tough, conductive-resistant nature of these crystals.
Key attributes of covalent crystals include:
Despite their robustness, covalent crystals generally do not conduct electricity. This is because there are no free electrons or ions to carry an electric current. Examples of covalent crystals include quartz (SiO$_2$) and diamond, both of which exemplify the tough, conductive-resistant nature of these crystals.
Key attributes of covalent crystals include:
- Strong covalent bonds throughout
- High melting points
- Poor electrical conductivity
Molecular Crystals
Molecular crystals are composed of molecules held together by relatively weak intermolecular forces, such as van der Waals forces or hydrogen bonds. These forces are much weaker than covalent or ionic bonds, so molecular crystals typically have low melting points and tend to be soft. They are often found as gases under room temperature, but crystallize when cooled.
Due to their structure and bonding, molecular crystals also do not conduct electricity. The absence of mobile charged particles means they cannot carry an electric current. Classic examples include dry ice (solid CO$_2$) and iodine (I$_2$), both of which are substances that subliminate directly from solid to gas upon heating.
In brief, molecular crystals are characterized by:
Due to their structure and bonding, molecular crystals also do not conduct electricity. The absence of mobile charged particles means they cannot carry an electric current. Classic examples include dry ice (solid CO$_2$) and iodine (I$_2$), both of which are substances that subliminate directly from solid to gas upon heating.
In brief, molecular crystals are characterized by:
- Weak intermolecular interactions
- Low melting points
- Non-conductivity
Metallic Crystals
Metallic crystals are formed by the arrangement of metal atoms in a lattice structure, bound by a "sea" of delocalized electrons. This electron sea is the key to understanding the unique properties of metallic crystals. These free-moving electrons allow metals to conduct heat and electricity efficiently. Additionally, they contribute to the malleability and ductility of metals, allowing them to be shaped without breaking.
The metallic bonding gives these crystals their characteristic luster and strength. Despite their strength, metals are typically not brittle; instead, they can be bent and drawn into wires. Copper (Cu) and iron (Fe) are classic examples of metallic crystals. Each illustrates the efficient conductive and malleable nature of these structures.
Key properties of metallic crystals include:
The metallic bonding gives these crystals their characteristic luster and strength. Despite their strength, metals are typically not brittle; instead, they can be bent and drawn into wires. Copper (Cu) and iron (Fe) are classic examples of metallic crystals. Each illustrates the efficient conductive and malleable nature of these structures.
Key properties of metallic crystals include:
- Excellent conductivity
- Malleability and ductility
- Metallic luster
