MTL 200 MIDTERM 1
Average Atomic Weight Formula
Aw= (percent/100)(atomic mass)
Pauli-Exclusion Principle
An atomic orbital may describe at most two electrons, each with opposite spin direction
elctropositive elements
give up valence electrons to become positive charged ions
electronegative elements
give up valence electrons to become negatively charged ions
electronegativity trend
increases across a period, decreases down a group
non-directional bond
magnitude of bond equal in all directions (ionic, metallic)
directional bond
may only exist in direction of one atom and another that partakes in electron sharing
(covalent bonding)
Ionic character equation
%IC= {1-exp(0.25)(XA-XB)^2} x 100
crystalline material
atoms are situated in repeating arrays over large atomic distances
unit cell
the smallest portion of a crystal lattice that shows the 3D pattern of the entire lattice
Face Centered Cubic (FCC)
- atom located at each corner and center of faces
- most common structure for many metals
, Cube edge length (a) for FCC
a= 2Rsqrt2
Number of atoms associated with each unit cell
N= Ni+ Nf/2+ Nc/8
Two important characteristics for packing structure
Atomic Packing Factor (APF) and Coordination Number
Coordination Number
number of touching atoms
coordination number of FCC, BCC, HCP, Simple cubic
FCC- 12
BCC- 8
HCP- 12
simple cubic- 6
atomic packing factor
The sum of the sphere volumes of all atoms within a unit cell divided by the unit cell volume.
APF = volume of atoms in a unit cell/ total unit cell volume (Vs/Vc)
APF for FCC, BCC, HCP
FCC- 0.74
BCC- 0.68
HCP- 0.74
BCC- Body centered cubic
atoms at eight corner and one in middle
unit cell length (a) for BCC
a= 4R/sqrt3
Number of atoms per unit cell (n) FCC, BCC, HCP, SImple cubic
FCC- 4
BCC-2
Average Atomic Weight Formula
Aw= (percent/100)(atomic mass)
Pauli-Exclusion Principle
An atomic orbital may describe at most two electrons, each with opposite spin direction
elctropositive elements
give up valence electrons to become positive charged ions
electronegative elements
give up valence electrons to become negatively charged ions
electronegativity trend
increases across a period, decreases down a group
non-directional bond
magnitude of bond equal in all directions (ionic, metallic)
directional bond
may only exist in direction of one atom and another that partakes in electron sharing
(covalent bonding)
Ionic character equation
%IC= {1-exp(0.25)(XA-XB)^2} x 100
crystalline material
atoms are situated in repeating arrays over large atomic distances
unit cell
the smallest portion of a crystal lattice that shows the 3D pattern of the entire lattice
Face Centered Cubic (FCC)
- atom located at each corner and center of faces
- most common structure for many metals
, Cube edge length (a) for FCC
a= 2Rsqrt2
Number of atoms associated with each unit cell
N= Ni+ Nf/2+ Nc/8
Two important characteristics for packing structure
Atomic Packing Factor (APF) and Coordination Number
Coordination Number
number of touching atoms
coordination number of FCC, BCC, HCP, Simple cubic
FCC- 12
BCC- 8
HCP- 12
simple cubic- 6
atomic packing factor
The sum of the sphere volumes of all atoms within a unit cell divided by the unit cell volume.
APF = volume of atoms in a unit cell/ total unit cell volume (Vs/Vc)
APF for FCC, BCC, HCP
FCC- 0.74
BCC- 0.68
HCP- 0.74
BCC- Body centered cubic
atoms at eight corner and one in middle
unit cell length (a) for BCC
a= 4R/sqrt3
Number of atoms per unit cell (n) FCC, BCC, HCP, SImple cubic
FCC- 4
BCC-2
