Lewis Structures

1. Lewis Structures • H is always a terminal atom • The atom with the lowed EN is the central atom • Find the total # of valence (ions add and lose electrons) • Bond each atom to the central atom with a single bond • Place lone pairs around terminal atoms to complete their octet • Add remaining electrons to central atom • Use multiple bonds to complete the octet of the central atom

2. Exceptions to the Octet Rule • Hydrogen only gets 2 • Boron is a moron, he likes 6 electrons • Expanded Valence – 3rd energy level or higher

5. HYBRID ORBITALS covalent bonds are formed by overlap of atomic orbitals atomic orbitals on the central atom can mix and exchange their character – hybridization ONLY sBONDS ARE FORMED FROM OVERLAP OF HYBRIDS ORBITALS ARE NOT FORMED FROM HYBRID ORBITALS

7. practice

8. 2 sp Hybrids Formed From an s and p

9. 3 sp2 Hybrids Formed From an s and 2 p’s

11. Forming sigma bonds • Three ways atoms can form a sigma bond: • 2 hydrogen atoms’ 1s orbitals overlap • a hybrid orbital overlaps a hydrogen’s 1s orbital • 2 hybrid orbitals overlap end-to-end

12. Forming pi bonds • Pi bonds form when • atoms are already bonded with a sigma bond • both atoms have a leftover p orbital • Pi bonds form when two atoms’ p orbitals overlap side-by-side

13. NO21- Resonance Structures   next formal charge

14. Delocalized pi bonding in CO3–2 • In the CO3–2 ion, one pi bond is delocalized over three C-O connections • The C atom and all three O atoms are sp2 hybridized and have a leftover p orbital • The four p orbitals overlap side-to-side to create the pi bonding

15. C6H6, Benzene an Important Molecule With Resonance Delocalized e- due to resonance explains why the bonds in benzene are identical.

16. AX2 EXAMPLE BH2 LINEAR

17. AX2 WITH DOUBLE BOND CO2

18. AX3 EXAMPLE BH3 TRIGONAL PLANAR

20. AX4EXAMPLE CH4

21. AX3E EXAMPLE NH3 PYRAMIDAL

22. AX2E2 EXAMPLE H2S BENT

23. AX5 EXAMPLE PCl5 TRIGONAL BIPYRAMIDAL

24. AX4E EXAMPLE SF4 SEE SAW

25. AX3E2 EXAMPLE BF3 T SHAPE

26. EXAMPLE XeF2 LINEAR

27. Next resonance

29. EXAMPLE SeF6 OCTAHEDRAL

30. EXAMPLE IF5 SQUARE PYRAMIDAL

31. EXAMPLE XeF4 SQUARE PLANAR

33. Polar molecules • A compound’s polarity can be measured experimentally as its dipole moment • Polar molecules align themselves with an electrical field – + + – + – + – – + – + + – + – + – – + – + + – + – + – – +

34. Polar molecules • The C=O bond is polar • But the dipole moment of CO2 is zero • CO2 is not a polar molecule

35. Examples SO2 • S-O bonds are polar • Geometry is bent (120°) • sp • Bond dipoles don’t cancel • SO2 is polar SO3 • S-O bonds are polar • Geometry is trigonal planar • sp2 • Bond dipoles do cancel • SO3 is nonpolar

36. Examples H2O • H-O bonds are polar • Geometry is bent (109.5°) • sp • Bond dipoles don’t cancel • H2O is polar OCl2 • O-Cl bonds are nonpolar • sp • OCl2 is nonpolar

37. SF4 • S-F bonds are polar • geometry is see saw • dsp3 • axial bond dipoles cancel • equatorial bond dipoles don’t cancel • SF4 is polar PF5 P-F bonds are polar • geometry is trigonal bipyramid • dsp3 • axial bond dipoles cancel • equatorial bond dipoles cancel • PF5 is nonpolar

38. XeF2 • Xe-F bonds are polar • geometry is linear • structural pair geometry is trigonal bipyrimidal • lone pairs in equatorial • F atoms in axial • dsp3 • bond dipoles cancel • XeF2 is nonpolar PbH2 • Pb-H bonds are nonpolar • PbH2 is nonpolar