1. Lewis (electron dot) structures show the electron domains in the valence shell and are used to predict molecular shape.

2. Lewis structure Coordinate bond/dative bond Electron deficient VSEPR theory Electron domain Electron domain geometry Linear Trigonal planar Bent Tetrahedral Molecular geometry Linear Tetrahedral Bent Trigonal pyramidal Trigonal planar Dipole moment Delocalized electrons Resonance Giant molecular Nanotechnology

3. Lewis structures are used for covalent molecules only Used to represent valence electrons Steps: 1. calculate total number of val. e- in molecule 2. draw skeletal structure of molecule 3. use crosses, dots or a line to show e- pairs 4. add e- pairs to complete the octets (H only has 2) 5. use double or triple bonds if necessary 6. check that the total number of e- is equal to #1

4. Notes: must add an e- for each negative charge (anion) or subtract one e- for each positive charge (cation) Square brackets are needed for ions

5. The bond is formed by one atom donating both e- to be shared An arrow is used to show the originating e- pointing to the atom that is being shared with

6. Two primary exceptions: Be and B These are called electron deficient and are often the receivers of coordinate bonds

7. Valence Shell Electron Pair Repulsion theory Electron pairs repel each other and will orient themselves as far away from each other as possible This is lower energy and more stable This is how the geometry is determined Electron pairs and bonded pairs are referred to as electron domains: Electron pair Single bond Double bond Triple bond

8. Total number electron domains around central atom will determine geometric arrangement Shape of molecule determined by angles between bonded atoms Lone pairs have higher concentration of charge and therefore cause stronger repulsion than bonded pairs Lone pair-lone pair > lone pair-bonding pair > bonding pair-bonding pair Molecules with lone pairs have some distortions due to higher charge repulsion Structures that do not have lone pairs ≠ Lewis structures

9. Electron domain geometry: linear Molecular geometry: linear

10. Electron domain geometry: trigonal/triangular planar Molecular geometry no lone pairs: trigonal/triangular planar Molecular geometry 1 lone pair: bent

11. Electron domain geometry: tetrahedral

12. 1. draw Lewis structure 2. count number of electron domains around central atom 3. determine e- domain geometry: 2 e- domains = linear 3 e- domains = triangular planar 4 e- domains = tetrahedral 4. determine molecular geometry from the number of bonding e- domains 5. consider extra repulsion caused by lone pairs and make adjustments

13. Bonds can be polar while the molecule is still not considered polar… what?? Whether a molecule is polar depends on Type of polar bonds Orientation of bonds (shape) If dipoles are equal in polarity AND symmetrically arranged: Charge separation cancels out polar bonds = non-polar

14. If bonds are different in polarity OR not symmetrically arranged: Dipoles will not cancel = net dipole moment (overall dipole in molecule) There is directionality in the bonds AND in the molecule!

15. Delocalized e- : electrons that are shared between more than 1 bonding position Spread out e- increases stability of molecule Occurs with molecules that have multiple bonds and the bond can be moved to another atom Example: Ozone (O3)

16. O3: how many bonds are on each oxygen? Are they equal or different strength? So the correct Lewis structure is: Resonance: more than 1 valid Lewis structure can be drawn for the molecule Resonance hybrid = liger It is both a lion and tiger at the same time! Not switching!

17. Draw a structure for each species showing the resonance hybrid. How many bonds are actually on each bond?

18. Benzene is special! Draw the resonance hybrid Resonance makes benzene super stable Relatively unreactive

19. Giant molecular = network covalent = macromolecular structure These are molecules of covalently bonded atoms that form giant structures (unlike the itty bitty methane CH4, for example) These have different properties than the smaller molecules

20. Allotropes: different forms of an element in the same state of matter Carbon solids can be in different forms Graphite Diamond Fullerene C60 Graphene All are made of only carbon atoms, but their structures are different and so have different properties

23. Graphene is a relatively new form of carbon but expensive! New conductive material: mix graphene with plastics Transistors can be faster and smaller than Si transistors Touch screens printed on plastic – light, flexible, almost unbreakable Supercapacitors (store charge) replacing batteries, use in cars and mobile devices Solar panels – graphene can be wrapped around surfaces such as clothing, furniture or vehicles Nanotechnology: atomic scale manipulation of matter Graphone: add H to graphene = variable magnetic properties Flourographene: add F to graphene = rippled structure can make for an insulator

24. Silicon is right under carbon and forms 4 bonds Second most abundant element in Earth’s crust (after O) This can form a diamond-like structure for Si in elemental state But in nature, tends to form silicon dioxide tetrahedral structures (sand/quartz/glass) Here, SiO2 is actually only empirical Properties: Strong Insoluble in H2O High melting point Non-conductor of electricity