Chapter 10 - Solids and Liquids Flashcards
Sections 10.1-10.5
Describe Hydrogen Bonding
An unusually strong dipole formed by the bonding of hydrogen and either Oxygen, Nitrogen, or Fluorine
What factors lead O N and F to form the strongest Hydrogen Bonds?
Relatively high eletronegativities and small size
Between which substances are London Dispersion Forces the strongest?
Nobel Gases or non-polar molecules
Under what conditions do LDFs exist under in Nobel Gases and non-polar molecules?
Either low temperatures or high pressures, when the molecules are in close proximity
What consequence do LDFs have on Nobel Gases and non-polar molecules?
Lower freezing points result, as molecules must be very close for the LDFs to have a large effect
Explain Polarizability
The probability of electrons temporarily aligning in a dipole in an atom
What is the trend of polarizability in a group?
It increases going down a group
Explain Surface Tension
A measure of a liquid’s resistance to an increase in its surface area
What is the significance of a concave meniscus?
It means that adhesive forces are stronger than cohesive forces
What is the significance of a convex meniscus?
It shows that cohesive forces are stronger than adhesive forces
Explain Capillary Action
The spontaneous process by which liquids rise upward in a narrow tube
What are Cohesive Forces?
Intermolecular forces acting between molecules of the same substance
What are Adhesive Forces?
Intermolecular forces occurring between molecules of two or more different substances
Explain the concept of Viscosity
Viscosity is a measure of a liquid’s resistance to flow
How do molecular complexity and hydrogen bonding contribute to viscosity?
Complex molecules cannot slide past each other as easily as planar molecules; hydrogen bonding creates strong dipoles which created unusually strong cohesive forces between molecules of the same substance
Explain the structure of Crystalline Solids
Highly regular structures consisting of 3-dimensional systems of points called lattices, held together at their vertices by small, repeating units called Unit Cells
What is the equation used for the x-ray analysis of solids?
nλ = 2d sin θ
Explain the key point where Ionic, Molecular, and Atomic Solids deviate
Ionic: Ions are located at the lattice points
Molecular: Covalently bonded molecules are located at the lattice points
Atomic: Atoms are located at the lattice points
Into which three subcategories can Atomic Solids be broken?
Metallic, Network, and Group 8A
Explain Metallic Solids
Delocalized covalent bonding holds metal atoms together at the lattice points
Explain Network Solids
Directional covalent bonding groups metal atoms into giant molecules, repeating 3-dimensional lattice structures
Explain Group 8A Solids
LDFs hold group 8A atoms together at lattice points
List some properties of metals
High thermal and electrical conductivity, malleability, ductility, high melting point
Explain Closest Packing structure
Each atom has 12 closest neighbors: 6 in the same layer, 3 above, and 3 below
Differentiate Hexagonal and Cubic Closest Packing
Hexagonal: aba - every other layer occupies the same vertical position
Cubic: abba- every fourth layer occupies the same vertical position
Describe Molecular Orbitals
Empty or partially filled valence electron orbitals of metal atoms through which electrons can flow
How do MOs explain conductivity?
Bands of MOs exist in metals, which allow electrons to be quickly shuttled through many atoms, forming a sea of mobile electrons
Describe an Alloy
A mixture of elements having overall metallic properties
How do the two types of Alloys, Substitutional and Interstitial, vary?
Substitutional: some atoms of the host crystal are replaced by atoms of another substance
Interstitial: small atoms of an added substance fit between the spaces of the host crystal
Into what category of solids do Carbon and Silicon fall?
Network Atomic Solids
What are the differences in structure between Diamond and Graphite?
Diamond: sp3 hybrid; Large energy gaps; No π bonds
Graphite: sp2 hybrid; Small energy gaps; Connective π bonds
Where do MO bands occur in Graphite?
Between sp2 hybridized layers, in the area where empty or partially filled π bonds interact
What bonds typically occur in Silicon-based molecules?
Si-O bonds; σ bonds occur between Si and O atoms
Describe Silicates
Polyatomic silicon-oxygen structures with metallic cations; often made of SiO4
What two phases do ceramic structures exist in?
Minute crystals and cement
Explain why Silicon is a Semiconductor
A few electrons can cross into MOs at standard temperature (298K) in Silicon
Explain Contact Potential
A buildup of charge based on the reduction of electron movement
Describe an n-type semiconductor
Adding a substance with more electrons that the host crystal to a mixture enables more electrons to be used for conduction through MOs
What is the difference between p-type and n-type regions?
p-type: surplus of electrons
n-type: lack of electrons (holes)
What reaction does adding like charge to a p-n junction produce? What is this called?
Both electrons and holes flow away from the like charge, moving away from the poles of charge, or Reverse Bias
What reaction is produced by adding opposite charge to a p-n junction? What is this called?
Both holes and electrons flow toward the opposite poles, producing electrical current, or Forward Bias
How does the term Rectifier correlate to p-n junctions?
p-n junctions create a pulsating current (one-directional) from opposing currents (multi-directional)
