QUIZ (UNIT CELLS)

• Unit Cell 


  This is the basic, repeating structural unit of a crystalline solid that serves as a building block for the entire crystal lattice. What is this called?
• Lattice point - Each of these points within a lattice grid represents the location of an atom, ion, or molecule, contributing to the overall stability of the crystal structure. What is this point called?
• Lattice

  In the context of crystal structures, this term refers to a three-dimensional arrangement where each point corresponds to an atom or molecule in the structure, contributing to the crystal’s shape and strength. What is this arrangement called?
• Body-Centered Cubic (BCC) -What term is used to describe a crystal structure with atoms at each corner and one in the center of the unit cell?
• The Body Diagonal - In a BCC unit cell, what geometric feature (e.g., edge, diagonal) is the contact between atoms found along?
• 1


  Identify the number of atoms located fully inside a single Body-Centered Cubic (BCC) unit cell.
• Atomic Packing Factor (APF)

  It is the sum of the sphere volumes of all atoms within a unit cell divided by the unit cell volume.
• Face-Centered Cubic (FCC) Structure It is a crystal structure with atoms located at each of the corners and the center of all the cube faces.
• Coordination Number 


  It is an important characteristic of crystal structure for metals wherein each atom has the same number of nearest-neighbor or touching atoms.
• Metallic Bond - This allows metallic crystals to be hammered into thin sheets and drawn into wires, allowing them to slide without breaking.
• Dipole-dipole Interactions - This occurs in molecular crystals wherein the molecules tend to align themselves so that the positive end of the molecule is near the negative end of another molecule. 
• Give one example of a covalent crystal. 

  Diamond or Quartz
• Sulfur - Zinc sulfide has a face centered cubic lattice where the _____ ions are located at the lattice points.
• X-ray Diffraction - It refers to the scattering of X-rays by the units of a crystalline solid. 
• Constructive Interference - A type of interference pattern that occurs when the waves are “in phase” or when it combines to amplify each other, creating bright spots. 
• Electron-Density Contour Map - It tells us the relative electron densities at various locations in a molecule. 
• Amorphous Solid


  It lacks a regular three-dimensional arrangement of atoms.
• Glass - Refers to an optically transparent fusion product of inorganic materials that has cooled to a rigid state without crystallizing.
• Pure Quartz Glass -Type of glass that is specifically used in optical research due to its low thermal expansion and transparency. 
• Van der Waals Force


  This is a weak attraction between molecules that occurs when a hydrogen atom is bonded to atoms like oxygen, nitrogen, or fluorine.
• Which of the following statements best describes a lattice in crystal structures?

  Answer:

  A 3D arrangement of repeating points where atoms, ions, or molecules are positioned
• Which of the following unit cell types is characterized by three unequal side lengths and all angles different from 90°?

  Answer: Triclinic
• In a Hexagonal Close-Packed (HCP) crystal structure, how many atoms are typically assigned to each unit cell?

  Answer. 6
• Which unit cell type is characterized by a close-packed arrangement and is commonly associated with metals like titanium and magnesium?

  
  

  Answer: Hexagonal Close-Packed (HCP)
• In a Body-Centered Cubic (BCC) structure, how many atoms are located within a single unit cell? Answer: 2
• Which of the following correctly represents the relationship between the unit cell length (a) and atomic radius (R) in a BCC crystal structure? Answer: 4R/Squareroot3
• The Body Diagonal - In the BCC structure, the atoms are in contact along which part of the cube?
• Which statement is true about the Body-Centered Cubic (BCC) and Simple Cubic (SC) crystal structures? Answer: BCC has an additional atom at the center, whereas SC does not.
• In FCC, the spheres or ion cores touch one another across a __________; the cube edge length (a) and the atomic radius (R) are related through __________. Answer: face diagonal;  2R√2
• What is the atomic packing factor for the FCC crystal structure?

  Answer: 0.74
• In a face-centered cubic (FCC) crystal structure, what is the coordination number, and how are the nearest neighboring atoms arranged around a front face atom?

  Answer: The coordination number is 12; each front face atom has four neighboring atoms in the same face, four atoms linked from behind, and four equivalent atoms positioned in the next unit cell.
• How many atoms may be assigned to a given FCC unit cell?

  Answer: 4 whole atoms
• Usually, ionic crystals cannot conduct electricity, but there are exceptions. The following are instances where NaCl (an ionic crystal) can conduct electricity EXCEPT: 


  Answer: when NaCl is heated at 701° C
• Which statement is true? 

  Answer: Graphite is used as a part of the printer that transfers ink onto the paper.
• Crystalline silicon has a cubic structure. The unit cell edge length is 543 pm. The density of the solid is 2.33 g/cm3. Calculate the number of Si atoms in one unit cell.

  Answer. 8
• When X-rays of wavelength 0.090 nm are diffracted by a metallic crystal, the angle of first-order diffraction (n = 1) is measured to be 15.2°. What is the distance (in pm) between the layers of atoms responsible for the diffraction?

  Answer: 172 pm
• The distance between layers in a NaCl crystal is 282 pm. X rays are diffracted from these layers at an angle of 23.0°. Assuming that n 5 1, calculate the wavelength of the X rays in nm.

  Answer: 0.220 nm
• What happens to the atoms in a solid when it solidifies rapidly?


  Answer: They become locked in random positions
• Glass acts more like a solid than a liquid. Formed by mixing molten silicon dioxide (𝑆𝑖𝑂2), with compounds such as sodium oxide (𝑁𝑎2𝑂), boron oxide (𝐵2𝑂3), and certain transition metal oxides for color and other properties.

  Answer: The first statement is false, while the second statement is true
• Which of the following is a common use for soda-lime glass?


  Answer: Windows and bottles