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Questions and Answers
Graphite is a type of ______ network solid made up of carbon atoms.
Graphite is a type of ______ network solid made up of carbon atoms.
covalent
Diamond and graphite are examples of ______ of carbon.
Diamond and graphite are examples of ______ of carbon.
allotropes
Molecular solids are held together by ______ forces.
Molecular solids are held together by ______ forces.
intermolecular
Most molecular solids are ______, while those with permanent dipoles are polar.
Most molecular solids are ______, while those with permanent dipoles are polar.
Molecular solids generally have ______ melting points compared to ionic solids.
Molecular solids generally have ______ melting points compared to ionic solids.
Sodium chloride (NaCl) is an example of an ______ solid.
Sodium chloride (NaCl) is an example of an ______ solid.
Most covalent network solids have ______ conductivity, except for graphite.
Most covalent network solids have ______ conductivity, except for graphite.
The ability of a single element to form multiple structures is known as ______.
The ability of a single element to form multiple structures is known as ______.
Crystalline solids are classified according to the type of forces that hold its particles together, including metallic, covalent network, molecular, and ______.
Crystalline solids are classified according to the type of forces that hold its particles together, including metallic, covalent network, molecular, and ______.
Metallic solids consist entirely of ______ atoms.
Metallic solids consist entirely of ______ atoms.
Metallic bonding involves a uniform distribution of atomic nuclei within a 'sea' of ______.
Metallic bonding involves a uniform distribution of atomic nuclei within a 'sea' of ______.
Covalent network solids are poor conductors and are typically characterized by strength, hardness, and high ______ points.
Covalent network solids are poor conductors and are typically characterized by strength, hardness, and high ______ points.
Covalent network solids are characterized by a network of ______ bonds that extend throughout the material.
Covalent network solids are characterized by a network of ______ bonds that extend throughout the material.
Diamond is made up of carbon atoms and is known as the hardest ______ material.
Diamond is made up of carbon atoms and is known as the hardest ______ material.
Metallic solids consist of positively charged ions surrounded by a sea of ______.
Metallic solids consist of positively charged ions surrounded by a sea of ______.
Molecular solids possess distinct ______ forces, such as Van der Waals forces or hydrogen bonding.
Molecular solids possess distinct ______ forces, such as Van der Waals forces or hydrogen bonding.
Molecular solids are usually characterized by ______ melting points compared to covalent network solids.
Molecular solids are usually characterized by ______ melting points compared to covalent network solids.
Allotropes are different forms of an element, an example of which is that diamond is an allotrope of ______.
Allotropes are different forms of an element, an example of which is that diamond is an allotrope of ______.
Allotropy refers to the existence of an element in more than one ______ form.
Allotropy refers to the existence of an element in more than one ______ form.
Some properties of metallic solids include high electrical and thermal conductivity, being malleable, and ______.
Some properties of metallic solids include high electrical and thermal conductivity, being malleable, and ______.
The types of crystals include ionic, covalent, molecular, and ______ solids.
The types of crystals include ionic, covalent, molecular, and ______ solids.
In a crystalline solid, the arrangement of ions or atoms creates a ______ structure.
In a crystalline solid, the arrangement of ions or atoms creates a ______ structure.
The unit cell is the smallest repeating unit of a crystal structure that defines its ______ properties.
The unit cell is the smallest repeating unit of a crystal structure that defines its ______ properties.
A crystal lattice represents the arrangement of ______ points in the unit cell.
A crystal lattice represents the arrangement of ______ points in the unit cell.
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Study Notes
Crystalline Solids Overview
- Crystalline solids are organized in a repeating pattern, held by strong intermolecular forces.
- Classification based on bonding types: metallic, covalent network, molecular, and ionic.
Covalent Network Solids
- Consist of atoms bonded by a network of covalent bonds.
- Examples: graphite (2D, good conductor) and diamond (3D, hardest known material, thermal conductor).
- Graphite forms flat sheets and is an allotrope of carbon, while diamond is renowned for its hardness.
Molecular Solids
- Comprised of covalently bonded atoms/molecules, held by intermolecular forces (e.g., van der Waals).
- Generally insulators, soft, and melting points vary significantly (e.g., ice: 0°C, sugar: 186°C, fullerene: 280°C).
- Polar molecules, like sugar, have higher melting points and are soluble in water.
Ionic Solids
- Made of cations (positive ions) and anions (negative ions), bonded through electrostatic attractions.
- Difficult to break and typically have high melting points, exemplified by sodium chloride (NaCl).
Metallic Solids
- Composed entirely of metal atoms with metallic bonding, characterized by a "sea" of delocalized electrons.
- Features include high electrical and thermal conductivity, malleability, ductility, and variable melting points.
- Examples include sodium and copper, which exhibit close-packed atomic arrangements.
Allotropy
- Refers to the ability of a single element to form multiple structural forms.
- Carbon has notable allotropes: diamond and graphite, each with unique properties.
Unit Cell Concepts
- The unit cell is the smallest repeating unit of a crystalline solid, defining the crystal structure.
- Crystal lattices and motifs are used to visually represent these structures.
- In 2D, a unit cell is typically a parallelogram; in 3D, it is a parallelepiped, with variations based on lattice points.
Lattice Structures
- 2D lattices have four primitive types: square, rectangular, hexagonal, and oblique.
- 3D lattices feature seven primitive types: cubic, hexagonal, tetragonal, rhombohedral, orthorhombic, monoclinic, and triclinic.
- Specific cubic lattices include primitive (lattice points at corners), body-centered (extra point at center), and face-centered (extra point at the center of faces).
Summary of Properties
- Covalent network solids are generally strong with high melting points but poor conductors (exception: graphite).
- Molecular solids exhibit variability in melting points and are typically insulators.
- Ionic solids are strong and have high melting points.
- Metallic solids are conductive with malleability and ductility, suitable for various applications.
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