ENGR 220 Lecture 3 Chapter 2
Week 2 Homework Problems Chapter 3 3.3, 3.6, 3.7, 3.14
Ionic Bonds
lonic bonding A. Predominant bonding in ceramics 1. Large difference in electronegativity B. Attraction occurs between + and - ions (Cations and Anions) 1. Requires electron transfer 2. Large difference in electronegativity required 3. Non-directional 4. Example NaCI C. For stability "nearest neighbors" 1. Opposite charges to attract or else they will repeal Energy of Interaction A. Potential Energy use Coulomb's Law 1. If potential energy is positive it is repulsive energy because they are the same sign 2. If potential energy is negative than it is an attractive energy B. Find minimum of the net energy equation to find the bond energy Bond Energy and Equilibrium A. Bond energy is the depth of the energy well B. Equilibrium is the distance or separation C. Minimum energy is the most table 1. Energy balance between attractive and repulsive terms Energy and Force vs. Distance A. Work in energy B. Work in forces 1. E= integral of force x distance
I1.
IV.
Covalent Bonds
V.
Covalent Bonding A. d 1. Share electrons to get stable octet of e^- B. Bonds determined by valence 1. S & p orbitals C. Structures are very symmetrical 8-N'Rule A. # of possible covalent bonds for atom = 8-N' B. N' is the number of valence of electrons Strong to weak A. Diamond: hard, high melting temp (>3,550 degrees celsius) B. Bismuth (pepto bismol): Low melting temp (270 degrees celsius) Typical in A. Non-metallic elemental molecules B. Molecules comprising dissimilar elements C. Polymers in the -C-C-C-C- backbone
VI.
VII.
VIII.
Weird Bond Hybridization
IX. X.
Associated with covalent bonding in C and other non-metallics sp^3 bond hybridization A. Combining (mixing) of 2 or more orbitals B. Results in orbitals "overlap" during binding C. Carbon: sp^2 Bond Hybridization A. One s orbital + two p orbitals hybridized B. Third p orbital (2pz) remains unhybridized C. Results in three equivalent sp2 hybrid orbitals in the same plane, 120 degrees between them (triangular)
XI.
Metallic Bonding
XII.
Metallic Bonding A. 1,2,3 valence electrons B. Electrons not bound to specific atoms C. Belong to metal as a whole D. Non-valence electrons and nuclei = ion cores E. Sea of valence electrons F. Z is # valence electrons per ion G. Non directional bond 1. Weak (hg) 2. Stron