CHEM 1415 1st EditionLecture 8Unit: Solids, Intermolecular Forces; LiquidsOutline of Current Lecture I. Solid StructuresII. MetalsIII. Intermolecular ForcesIV. LiquidsCurrent Lecture Solid Structureso Phase diagram Map showing which state of the element will be most stable at a given combination of temperature and pressureo Crystalline Structures Regular, repeating geometric arrangements o Amorphous Structures Substances could solidify into random arrangementso Packing Efficiency Represents the percentage of space that is occupied in an arrangement Increase in packing efficiency puts more atoms into the same volume Hexagonal close-packing (hcp) – third layer of atoms is directly over the first layer, 74% of the available space Cubic close-packing (ccp) – the third layer is offset, 74% of available spaceo Unit cell Smallest collection of atoms that displays all of the features of the structureo Body-centered cubic structure Atoms at the corners of the cube but now atoms is placed at center of thecube instead of the center of each face, 68% of the spaceo Simple cubic Central atom is missing, edge length of the cube becomes equal to the diameter of one atom, allowing the corner atoms to touch one anothero Coordination number Number of atoms immediately adjacent to any given atom Simple cubic structure has a coordination number of 6These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. Body centered cubic structure has a coordination number of 8 Metalso Malleable Can be formed into useful shapes or foilso Ductile Can be pulled into wireso Sea of electrons model Simplest way to explain metallic bonding Valence electrons of metal atoms are delocalized and move freely throughoutth solido Band theory Quantitative model for metallic bondingo Bonding molecular orbital a resulting wave with increased amplitude between the nucleio Antibonding molecular orbital If the orbitals interact out of phase, the resulting wave will have a node between the nucleio Valence band Band populated by valence electrons o Conduction band Lies directly above the valence band in energy Highest energy level is at the boundary between the conduction and valence bands An electron sitting at the top of the valence band needs only a little more energy band to move to the conduction bando Doping  Carefully controlled amounts of another element are combined with semiconductors Intermolecular forceso The forces between moleculeso Dispersion forces Instantaneous dipole – the average position of electrons is consistently a spherical shape, however, there is a fluctuation of charge due to the instantaneous location of electrons around the nucleus, creating a small transient positive charge and then a small transient negative charge induced dipole – created when an external electric field comes into contact with the molecule, causing the electrons to move away from the external negative chargeo polarizability a molecules’ charge distribution is easily affected by external fields measures the interactions between molecules large molecules are more polarizable than smaller oneso Hydrogen bonding Not actual bonding but strong dipole-dipole interactions The strongest of all intermolecular interactions Hydrogen atom pairs with highly negatively charged atom such as nitrogen, oxygen or fluorine Liquidso Atoms and molecules have a much greater mobility than in solidso Constant movement makes them excellent solventso Vapor pressure Gas phase pressure of a substance in equilibrium with the pure liquid in a sealed container Volatile – liquids with high vapor pressures, causes them to evaporate quicklyo Dynamic equilibrium Process where the state of a system remains constant but molecules are still escaping and being captured by the liquido Normal boiling point Temperature where the vapor pressure of the liquid is equal to one atmosphere Water boiling point is 100 ℃o Surface tension The edge of the liquid where the molecules find themselves in a state of high energy  Naturally minimizes the number of molecules in the largest volume, causing an observable bend at the liquid’s surface Cohesion: liquid – liquid interactions Adhesion: liquid – solid