chapter 12 (exam 1) Flashcards
(58 cards)
solids put into two categories
crystalline solids
amorphous
crystalline solids
composed of atoms or molecules arranged in structures with long range order (repeating pattern)
amorphous solids
disorder in structure
crystal lattice
3-D arrangement of atoms, ions, molecules with crystalline solid
unit cell
the crystalline lattice with the smallest collection of atoms or molecules
when the unit cell is repeated over and over
a crystal lattice is produced
lattice points
-represent the location of atoms or ions
-each lattice point has an identical environment
structure of crystalline solid is defined by
-the size and shape of the unit cell
-the location of atoms within a unit cell
cubic unit cell characterized by
equal length and 90 degree angle corners
-volume=a^3
simple cubic unit cell
-eight cubes meet at the corner so only 1/8 of that corner atom is within any one unit cell
simple cubic unit cell length of edge
2r
simple cubic unit cell contains ____ atoms
only one
body-centered cubic (BCC) unit cell
consists of a cube with one atoms at each corner and one atom in the very center of the cube
length of edge for BCC (not important)
4r/√3
BCC contains ____ atoms per unit cell
2 atoms
Face-centered (FCC) unit cell
consists of a cube with one atom at each corner and one atom in the center of each face
(FCC) two cubes meet so ___
-only 1/2 of that face atom is within any one unit cell
FCC consists of ___ atoms
4 atoms
length of edge of FCC (not important)
2√2r
coordination numbers
the number of ions or atoms that immediately surround an atom or ion of interest
simple cubic unit cell CN
6
BCC CN
8
FCC CN
12
molecular solids
-the lattice sites are occupied by molecules
-STRONG covalent bonds within the molecules and WEAKER IMF btw molecules
-moderately low melting points
