Structures of Solids Quiz

Structures of Solids

• Solids can be crystalline or amorphous.
• Crystalline solids have ordered atomic arrangements, flat surfaces, and definite angles.
• Amorphous solids lack orderly structure.

Unit Cells

• The repeating unit in a crystalline solid is the unit cell.
• Unit cells can be chosen in various ways, but the smallest one that clearly shows symmetry is usually selected.
• Crystalline solids can be represented by a 3-dimensional array of points called a crystal lattice.

Cubic Unit Cells

• Primitive cubic: Lattice points only at the corners.
• Body-centered cubic: Lattice points at the corners and the center of the cell.
• Face-centered cubic: Lattice points at the corners and the center of each face.

Bonding in Solids

• Molecular solids: atoms or molecules held together by intermolecular forces (e.g., London dispersion, dipole-dipole, hydrogen bonds). Soft, low melting points.
• Covalent network solids: atoms held together by strong covalent bonds in extended networks or chains. Hard, high melting points. Examples include diamond, quartz, silicon carbide.
• Ionic solids: positive and negative ions held together by electrostatic attraction. Hard, brittle, high melting points. Examples include NaCl, CaCO3.
• Metallic solids: metal atoms held together by delocalized valence electrons (electron sea model). Good conductors, malleable and ductile, wide range of melting points varying with number of valence electrons.

Close Packed Structures

• Close packed layers are the most efficient arrangement of spheres in terms of volume.
• The most efficient types of close packing are hexagonal close packing (HCP) and cubic close packing (CCP or FCC).
• HCP and CCP are 74% efficient, compared to the other types of structures.

Crystal Structure of Metals

• Metals can have hexagonal close-packed, cubic closed-packed or body-centered cubic structures.
• Each atom typically has 8 or 12 adjacent atoms.
• The bonding in metals is strong due to a 'sea' of delocalized valence electrons.

Density Calculations

• Density depends on crystal structure and the number of atoms in the unit cell.
• Calculations involve mass, volume, number of atoms and Avogadro's number.

Test your knowledge on the various structures of solids, including crystalline and amorphous forms. Explore the concept of unit cells and different types of cubic unit cells, as well as the bonding in solids. This quiz is essential for understanding the fundamental principles of solid-state chemistry.