Bonding 3 Flashcards
Seven types of crystal systems
Cubic, tetragonal, hexagonal, rhombohedral, orthorhombic, monoclinic, triclinic
Cubic NaCl
Cell edges: a = b = c
Cell angles: alpha = beta = gamma = 90 degrees
Tetragonal Hg(CN)2
Cell edges: a = b x= c
Cell angles: alpha = beta = gamma = 90 degrees
Hexagonal PbI2
Cell edges: a = b = c x= d
Cell angles: alpha = beta = gamma = 120 degrees
The edge d is perpendicular to the plane described by a, b, and c
Rhombohedral NaNO3
Cell edges: a = b = c
Cell angles: alpha = beta = gamma x= 90 degrees
Orthorhombic K2CrO4
Cell edges: a x= b x= c
Cell angles: alpha = beta = gamma = 90 degrees
Monoclinic K3Fe(CN)6
Cell edges: a x= b x= c
Cell angles: alpha = gamma = 90 degrees, beta x= 90 degrees
Triclinic CuSO4•5H2O
Cell edges: a x= BCM = c
Cell angles: alpha x= beta x= gamma
Simple cubic primitive unit cell (P)
Contains only atoms at the corners
Body-centered unit cell (bcc)
Contains atoms at the corners as well as at the center of the unit cell
Face-centered unit cell (FCC)
Contains atoms at its corners and in the center of each face
Four types of crystalline solids
Ionic solids
Covalent solids
Molecular solids
Metallic solids
Ionic solids
Made of (+) & (-) ions arranged in regular arrays; each job is surrounded by ions of the opposite charge Hard brittle, and have high melting and boiling points; poor conductors of electricity
Covalent solids
Made of atoms held together by very strong covalent bonds; very hard and high melting points; usually poor conductors of heat and electricity
Molecular solids (H2O, sucrose, I2, P4)
Made of neutral atoms; held together by dipole forces or dispersion forces; soft and poor conductors of heat and electricity
Metallic solids
Are made of one closely packed metal element; free valence e- circulate soured metallic cations making them goof electricity and heat conductors; high melting points
Close-packed structures
When in some substances, the atoms are packed together as closely as possible
Tetrahedral hole (t-hole)
Void created four spheres (3 in the 1st and 1 above) create a regular tetrahedron
Octahedral holes (o-holes)
Six spheres (3 in 1st layer and 3 in 2nd layer with layers offset by 60 degrees)
Triangular hole
Between 3 adjacent spheres in the same layer
Size of holes
Triangular< tetrahedral< octahedral
Hexagonal close packing
When sphere of 3rd layer lie directly above spheres of 1st layer
If there are N atoms jn a crystal
There are N O-holes and 2N T-holes
Cell volumes and length cubic-close packing
L = 2r V = L^3 = 8r^3
Cell volumes body-centered cubic cell
L = (4/sqroot(3))r V = ((4/sqroot(3))r)^3 = (64/3•sqroot(3))r^3
Cell volume face centered cell
L = (4/sqrt(2))r V = ((4/sqrt(2))r)^3 = (32/sqrt(2))r^3
Coordination number (CN)
The number of an atom or ion’s closest neighbors within the lattice; 1-6; smaller the surrounding atom and larger the center atom usually the higher the CN
Cohesive energy
The difference in energy between free ions and a solid
Lattice energy
The sum of the energies of interaction of the ions in a crystal
Madelung constant
Compressibility data that is used to theoretically evaluate the coulombic interactions in a lattice
Born-Haber Cycle
A calculation of the total energy of a crystal determined by considering all of its formation steps and including the lattice energy contribution
