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Questions and Answers
What is the characteristic of the atomic arrangement in a crystalline solid?
What is the primary function of the unit cell in describing crystal structure?
What distinguishes a polycrystalline solid from an amorphous solid?
What is the characteristic of the electrical conductivity of an ionic solid?
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How do the atoms or molecules in an amorphous solid arrange themselves?
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What is the characteristic of the hardness of a metallic solid?
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What is the characteristic of the melting point of a covalent solid?
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What is the primary difference between a crystalline solid and an amorphous solid?
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What is the scientific term for a finite array of points in three-dimensions in which every point has an identical environment as any point in the array?
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What is the type of bond that involves the sharing of a pair of valence electrons by two atoms?
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What is the law that presents a simple explanation of the diffracted beams from a crystal?
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What is the term for a solid that is not arranged in a regular order, as are those in crystalline solids?
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What is the type of defect that consists of a vacancy and an interstitial pair?
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What is the method that is useful for studying samples that are difficult to obtain in single crystal form?
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What is the type of crystal system that has a ≠b ≠c and α ≠β ≠γ ≠90?
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What is the term for a region of atomic disorder in a lattice only a few atomic diameters wide?
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What is the type of symmetry operation that combines a rotation with a reflection at a plane perpendicular to the rotation axis?
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What is the term for the symbolic vector representation for the orientation of an atomic plane in a crystal lattice?
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What is the number of atoms in a simple cubic unit cell?
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What is the number of atoms in a face-centered cubic unit cell?
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Which type of crystalline solid consists of atoms held together by intermolecular forces?
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What is the advantage of X-ray diffraction in determining the structure of crystalline materials?
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What is the symmetry operation that involves reflection through a plane?
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What is the type of crystalline solid that consists of positive cores of atoms held together by a surrounding sea of electrons?
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What is the disadvantage of X-ray diffraction in determining the structure of crystalline materials?
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What is the number of atoms in a body-centered cubic unit cell?
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Study Notes
Types of Solids
- Molecular solids: consist of atoms or molecules held together by intermolecular forces, e.g., dry ice (CO2)
- Metallic solids: consist of positive cores of atoms held together by a surrounding sea of electrons, e.g., copper, iron
- Ionic solids: consist of cations and anions held together by electrical attraction, e.g., NaCl
- Covalent solids: consist of atoms held together by a large network or chains of covalent bonds, e.g., diamond, graphite
Properties of Solids
- Melting point: variable for ionic solids, high to very high for metallic solids, very high for covalent solids
- Hardness: soft for molecular solids, malleable for ionic solids, hard for metallic solids, very hard for covalent solids
- Electrical conductivity: nonconducting for molecular solids, conducting for ionic solids, nonconducting for metallic solids (solid), conducting for metallic solids (liquid), usually nonconducting for covalent solids
Crystalline Solids
- Crystalline solids: have a regular arrangement of atoms, have a periodic structure, and have a high degree of order over many atomic distances
- Amorphous solids: do not have a regular arrangement of atoms, are made up of randomly oriented atoms, and have a low degree of order
- Polycrystalline solids: have a high degree of order over many atomic distances, but are made up of many small crystals or grains
Unit Cell
- The unit cell is the basic structural unit or building block of the crystal structure
- The unit cell is the smallest unit of a crystal that, if repeated, could generate the whole crystal
- The unit cell has a lattice parameter that describes the crystal structure
X-Ray Diffraction
- X-ray diffraction is a nondestructive technique used to study crystal structures
- Uses: differentiation between crystalline and amorphous materials, determination of the structure of crystalline materials, determination of the orientation of single crystals, determination of the texture of poly-grained materials
- Advantages: cheapest, most convenient, and widely used method, not absorbed very much by air
- Disadvantages: does not interact very strongly with lighter elements
Cubic System
- Simple cubic: has one atom per unit cell
- Body-centered cubic: has two atoms per unit cell
- Face-centered cubic: has four atoms per unit cell
Symmetry Operations
- Symmetry operations: operations that take the crystal into itself
- Types of symmetry operations: rotation, reflection, inversion, rotation-inversion, glide reflection, screw translation
Crystal Defects
- Types of defects: vacancy, interstitial, Frenkel, Schottky, edge dislocation, screw dislocation
- Frenkel defect: a combination of vacancy and interstitial defects
- Schottky defect: a cation vacancy – anion vacancy pair
- Edge dislocation: a type of dislocation where the Burger vector is perpendicular to the dislocation line
- Screw dislocation: a type of dislocation where the Burger vector is parallel to the dislocation line
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Description
This quiz covers the characteristics of different types of solids, including their melting points, hardness, and electrical conductivity. Identify the properties of molecular, ionic, metallic, and covalent solids.
