MOLECULES AND MATERIALS Flashcards
three forms of the element carbon
Graphite, diamond, and fullerenes
___________ was named buckminsterfullerene due to its resemblance to geodesic domes
popularized by the architect ___________
C60, Buckminster Fuller
Fullerenes were discovered in _______ in the form of C60
1985
Carbon has long been used as a material in important applications
- Diamond is used in drill bits and jewelry
- Graphite is used in pencils, as a lubricant, and as a composite material
- Applications of fullerenes and nanotubes are still being explored
are maps showing which state or phase of a compound or an element will be most stable at a given combination of pressure and temperature
Phase Diagrams
The state or phase of a compound can be manipulated by changing
the temperature and pressure of the compound
Note that pressure is shown on a
______ scale
logarithmic
are a type of fullerene that have remarkable properties
Nanotubes
What property of carbon nanotubes might lead to interesting engineering
applications?
* Resistance to reactions
* Tensile strength
* Elasticity
- Tensile strength
Atoms or molecules arrange themselves into two types of solids
Crystalline solids
Amorphous solids
Atoms or molecules that assume a regular, repeating geometric arrangement
Crystalline solids
Atoms or molecules that assume a random arrangement
Amorphous solids
in crystalline solids, it is the percentage of space occupied in a given arrangement
Packing efficiency
- The less empty space in the packing of atoms or molecules in a solid, the higher the packing efficiency
- The higher the packing efficiency, the higher the density of a solid
Two ways to maximize packing efficiency
hexagonal close-packing or hcp
cubic close-packing or ccp
the third layer can be stacked directly above the atoms in the first layer
hexagonal close-packing or hcp
if the third layer can be stacked directly above the hollows in the first layer
cubic close-packing or ccp
is the smallest collection of atoms that displays all the features of a crystal structure
unit cell
Three types of cubic unit cells
simple cubic or sc
body-centered cubic or bcc
face-centered cubic or fcc
1/8 each of eight corner atoms
simple cubic
containing one additional atom within
body-centered cubic
with an additional ½ each of six atoms along the faces
face-centered cubic
How much does each atom at the corner of a cubic unit cell contribute to that
unit cell?
* 1 atom
* 1/4 atom
* 1/8 atom
* 1/12 atom
1/8 atom
Calculation of Packing Efficiency
fcc = 1/2 (# of fc) + 1/8 (# of corner) = 4
bcc = (# of bcc) - 1/8 (# of corner) = 2
sc = 1/8 (# of corner) = 1
is the number of atoms immediately adjacent to any given atom
Coordination number
Condensed Phases—Solids
- Simple cubic structure has a coordination number of __
- Body-centered cubic structure has a coordination number of __
- Close-packed structures, ccp and hcp, have coordination numbers of __
6, 8, 12
are the attractive and repulsive forces between molecules
Intermolecular forces
responsible for determining the structure and properties of condensed phases
Intermolecular forces
are common to all molecules
Dispersion forces
Dispersion forces are also called
London Forces
Dispersion forces are also referred as
instantaneous dipole–induced dipole forces
exist for two oppositely charged points separated by some distance
Dipoles