Structure and Bonding

1. Chapter 1 Structure and Bonding Suggested Problems - 1-17,23-4,30,36,43,56,57

2. What is Organic Chemistry? • Organic compounds: from living organisms (with a vital force) • Inorganic compounds: from minerals (without a vital force) organic chemistry = compounds that contain carbon

3. Carbon Compounds Are Ubiquitous • Living things are made of organic chemicals • Proteins – hair, cell structures • Nucleic Acids -genetic make-up • Carbohydrates & fats - energy • Medicines

4. What Makes Carbon So Special? • Atoms to the left of carbon give up electrons. • Atoms to the right of carbon accept electrons. • Carbon shares electrons.

5. The Structure of an Atom Protons are positively charged. Neutrons have no charge. Electrons are negatively charged. Atomic number = # of protons Atomic number of carbon = 6 Neutral carbonhas six protons andsix electrons.

6. Isotopes

7. The Distribution of Electrons in an Atom • The first shell is closest to the nucleus. • The closer the atomic orbital is to the nucleus, the lower its energy. • Within a shell, s < p.

8. Relative Energies of the Atomic Orbitals We will not be utilizing d orbitals in this course.

9. Shapes of Atomic Orbitals

10. -Aufbau principle: An electron goes into the atomic orbital with the lowest energy. -Pauli exclusion principle: No more than twoelectrons can be in an atomic orbital. -Hund’s rule: An electron goes into an emptydegenerateorbital rather than pairing up.

11. Atoms on the Left Side of the Periodic Table Lose an Electron

12. Atoms on the Right Side of the Periodic Table Gain an Electron

13. An Ionic Bond is Formed by the Attraction Between Ions of Opposite Charge

14. Covalent Bonds are Formed by Sharing Electrons Nonpolar covalent bond = bonded atoms are the same Polar covalent bond = bonded atoms are different

15. Bond Polarity Depends on the Difference in Electronegativity 2.0 0.5

16. Polar Covalent Bonds

17. Dipole Moments the greater the difference in electronegativity, the greater the dipole moment, and the more polar the bond

18. Electrostatic Potential Maps

19. Formal Charge Formal Charge = # of valence electrons – (# of bonds + # of lone-pair electrons)

20. How Many Bonds Does an Atom Form?

21. Neutral Carbon Forms Four Bonds if carbon does not form four bonds, it has a charge (or it is a radical)

22. Neutral Nitrogen Forms Three Bonds Nitrogen has one lone pair. If nitrogen does not form three bonds, it is charged.

23. Neutral Oxygen Forms Two Bonds Oxygen has two lone pairs. If oxygen does not form two bonds, it is charged.

24. Hydrogen and the Halogens Form One Bond A halogen has three lone pairs. if hydrogen or halogen does not form one bond, it has a charge (or it is a radical)

25. The Number of Bonds and Lone Pairs • Halogen = 3 lone pairs • Oxygen = 2 lone pairs • Nitrogen = 1 lone pair You might want to know this

26. Lewis Structures

27. How to Draw a Lewis Structure NO3– Determine the total number of valence electrons (5 + 6 + 6 + 6 = 23). Because they are negatively charged, add another electron = 24. Avoid O–O bonds. Check for formal charges.

29. Kekulé Structures and Condensed Structures

30. What is an Atomic Orbital?

31. The Lobes of a p Orbital Have Opposite Phases

32. The Three p Orbitals

33. The Bonding in H2 • A covalent bond forms when two atoms approach each other closely so that a singly occupied orbital on one atom overlaps a singly occupied orbital on the other atom • Two models to describe covalent bonding. Valence bond theory, Molecular orbital theory Valence Bond Theory: • Electrons are paired in the overlapping orbitals and are attracted to nuclei of both atoms • H–H bond results from the overlap of two singly occupied hydrogen 1s orbitals • H-H bond is cylindrically symmetrical, sigma (s) bond

34. The Bonding in H2 Molecular Orbital Theory: • Covalent bonds result when atomic orbitals combine to form molecular orbitals. • In analogy to an atomic orbital, a molecular orbital describes the volume of space around a molecule where an electron is likely to be found. • -- An atomic orbital surrounds an atom; a molecular orbital surrounds a molecule.

36. Waves Can Reinforce Each Other; Waves Can Cancel Each Other

37. Atomic Orbitals Combine to Form Molecular Orbitals

38. Side-to-Side Overlap of In-Phase p Orbitals Forms a π Bond

39. The Bonding in Methane

40. In Order to Form Four Bonds,Carbon Must Promote an Electron

41. Four Orbitals are Mixed to Form Four Hybrid Orbitals An sp3 orbital has a large lobe and a small lobe.

42. The Carbon in Methane is sp3 Carbon is tetrahedral. The tetrahedral bond angle is 109.5°.

43. The Bonding in Ethane

44. The Bonding in Ethane

45. End-On Overlap of Orbitals Forms a (σ) Bond

46. Bonding in Ethene

47. An sp2 Carbon Has Three sp2 Orbitals and One p Orbital

48. The Carbons in Ethene are sp2

49. Bonding in Ethyne

50. The Two sp Orbitals Point in Opposite Directions The Two p Orbitals are Perpendicular