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Announcements
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Exam Friday.
Review Materials
Posted.
Graded quizzes available outside Dr. Gutow's
office.
If you instructor has not previously arranged
to return your lab notebooks they are outside
Dr. Gutow's office.
Review
• Molecular solids=Isolated molecules held together
by intermolecular forces.
• Network solids
– diamond = continuous network of covalent bonds.
– Silicates = networks of SiO4 tetrahedra held together
by ionic interactions (ex. minerals and clays).
• band structure of solids
– Conductors, semiconductors and non-conductors.
– Shift in band gap caused by small amounts of
impurities (ex. yellow diamond).
• Intro to crystal field splitting in discussion.
Some Silicate Gemstones
courtesy of Dr. Wacholtz
Tourmalines
(Na,Ca)(Mg, Fe, Al, Mn, Li)3Al6(BO3)3(Si6O18)(OH,F)4
Beryls
Be3Al2-x(Cr, Fe)xSi6O18
Absorbance of Emeralds
(fig 10.25)
Zn2+ tetrahedral complexes
Courtesy of Dr. Wacholtz
Wavelength
Transmitted/
reflected
Wavelength
Absorbed
(d-d) transition
~565 nm
~580 nm
~605 nm
~600
~610
~640
(note the ligands absorb in the UV to blue range 350-400 nm
Review-Chapter 9
• attractive interactions among molecules:
– ion-ion (lattice energy: U=k(Q1Q2/d), calculation of U
from a cycle of reactions)
– ion-dipole
– dipole-dipole
– dipole - induced dipole
– Dispersion
• H-bonding
Review-Chapter 9
– Generally weaker than ion-ion interactions
– Stronger than other intermolecular interactions.
– Only seen for hydrogens bonded to N, O or F.
– Bond to lone pair on another molecule (usually on N,
O or F).
– Explain very high boiling points for H2O, NH3 and HF
• Solubility
– “like dissolves like” (polar in polar, nonpolar in
nonpolar)
– Only soluble if dissolved particles lower energy than
undissolved solid.
Review-Chapter 9
• Raoult’s law: Pvap = XsolvP˚solv
• Note: Xsolv=nsolv/(nsolv + insolute)
• Reading phase diagrams
• Water’s unusual properties explained primarily
by strong directional hydrogen bonding.
– expansion on freezing
– surface tension
– formation of a meniscus
– capillary action
Review-Chapter 10
• Crystalline solids
– cubic, bcc and fcc lattices
●
– Volumes of different lattices in terms of radius of
atoms:
Vcubic = 8r3,
– In ionic lattices smaller ion usually fits into octahedral
or tetrahedral holes
• small (+) ion < 44% radius of big ion into tetrahedral
holes
• if (+) ion about same size as (-) ion get simple cubic,
like CsCl.
Review – Chapter 10
• Molecular solids=Isolated molecules held together
by intermolecular forces.
• Network solids
– diamond = continuous network of covalent bonds.
– Silicates = networks of SiO4 tetrahedra held together
by ionic interactions (ex. minerals and clays).
• band structure of solids
– Conductors, semiconductors and non-conductors.
– Shift in band gap caused by small amounts of
impurities (ex. yellow diamond).
Review – Chapter 10
• Crystal field theory
– Ligands around a transition metal ion cause the
d-orbitals to lose their degeneracy.
– You are responsible for two ligand arrangements,
octahedral
tetrahedral
– High spin versus low spin states.