Ch. 12 ---Chemical Bonding

1. Sharing Ch. 12---Chemical Bonding one pair 2 4 6 Covalent Bonds ____________ electrons between two atoms in order to fill the outer energy level (or shell) Each bond involves the sharing of _____ _________ of electrons. Single Bonds= __ e-’s Double Bonds= __ e-’s Triple Bonds=__ e-’s

2. ↑ ↑ ↓ ↑ ↓ ↑ ↑ ↓ ↑ Ways to Represent Covalent Bonds in Compounds “Circled Arrows” for bonds. a) H2 H ___ 1s H ___ 1s b) F2 F …___ ___ ___ ___ 2s 2p F …___ ___ ___ ___ 2s 2p ↓ ↑ ↓ ↑ ↑ ↓ ↑

3. ↓ ↑ ↑ ↑ ↑ ↑ ↑ ↑ H ___ 1s H ___ 1s H ___ 1s ↓ ↑ ↓ ↑ ↑ ↑ c) NH3 N …___ ___ ___ ___ 2s 2p d) H2O O …___ ___ ___ ___ 2s 2p ↑ ↑ H ___ 1s H ___ 1s

4. H:H .. .. .. .. :F:F: .. .. .. .. · · · · :N::N: Ways to Represent Covalent Bonds in Compounds (2) “Dots” for bonds. (Lewis Structures) a) H2 H · + · H b) F2:F· + ·F:  c) N2 :N · + ·N:  (triple bond) d)NH3 · · .. H:N:H .. H

5. H–H .. .. :F–F: .. .. :N≡N: ¨ H–N–H ׀ Ways to Represent Covalent Bonds in Compounds (3) “Lines” for bonds. a) H2 b) F2 c) N2 d)NH3 e) H2O H .. H–O: ׀ H

6. Coordinate Covalent Bonds • Both of the electrons that make the bond come from the ________ _______________ . • Example: CO (carbon monoxide) same element C …___ ___ ___ ___ 2s 2p ↓ ↑ ↑ ↑ ↑ ↓ O …___ ___ ___ ___ 2s 2p ↓ ↑ ↑ ↑ .. :C O: .. .. Two of the bonds are “normal”, and the third bond is a coordinate covalent bond. – :C O: – ←

7. ↓ ↑ ↑ ↑ C …___ ___ ___ ___ (After: 4 covalent bonds available) ↑ ↓ ↑ ↑ ↑ 2sp3 Practice Problem: Draw CH4 using arrows, dots, and lines for bonds. Carbon’s Hybrid Orbital C …___ ___ ___ ___ (Before) 2s 2p C …___ ___ ___ ___ ↑ ↑ ↑ ↑ 2sp3 ↑ H ___ 1s ↑ ↑ H ___ 1s ↑ H ___ 1s H ___ 1s

8. two The 7 Diatomic Elements pair elemental halogens Some elements will covalently bond to themselves to form a molecule composed of ____ atoms. These elements are never found in nature as single atoms. Instead, they will be bonded as a ________ when they are in the “_________________” state. The 7 diatomic elements are the gases H, O, N, and all of the _________________, (Group 7A). H2, O2, N2, Cl2, Br2, I2, F2 “HONClBrIF”

10. Air contains N2 and O2 molecules.

11. The decomposition of two water molecules

12. 8 8 noble gas 2 Octet Rule Atoms want ___ e-’s in their outer shell when forming compounds. This will mean ___ dots around them all together. This is the stable e- configuration of a __________ _______! Important exception: Hydrogen = only needs __ to be full (like He). Other Exceptions: PCl5 (___ e-) SF6 (___ e-) BF3(___e-) 10 12 6

13. Resonance Resonance is the ability to draw 2 or more different e- dot notations that obey the octet rule. Examples: O3 (ozone) and SO2 Practice Problem: Draw the resonance structures for CO3-2.

14. tetrahedral VSEPR Theory: Molecular Shapes pyramidal Most shapes are based on a __________________. Examples:CH4 CCl4 Removing the top of the tetrahedral makes the ________________ shape. Examples:NH3PCl3

15. bent VSEPR Theory: Molecular Shapes linear Removing one side of the pyramid makes the _____________ shape. Examples:H2O H2S If there are only two atoms bonded, it is ______________. Examples:O2 HCl CO2 (linear because of its double bonds.)

16. 3 plane VSEPR Theory: Molecular Shapes Another we will need to know is called “trigonal planar”. “Trigonal” means that the central atom is bonded to ___ other atoms. “Planar” means that the 3 atoms all lie in the same ______________. Example:BF3 (Notice that Boron will only have ___ e-’s around it. The missing pair of electrons will make it planar instead of ________________.) 6 pyramidal

17. VSEPR Theory: Molecular Shapes Trigonal bipyramid Octahedral Finally, the last 2 shapes occur when there are 5 or 6 regions of electrons are around the central atom. (These molecules are also exceptions to the octet rule!) ___________________ (5 electron domains) __________________ (6 electron domains) Examples:PCl5 and SF6

18. electronegativity Polar and Nonpolar Bonds equal unequal transfer Even though the electrons in a covalent bond are shared, sometimes the attraction for the bonded pair, (the _____________________), is uneven. This gives rise to 3 bond types. nonpolar covalent bonds: ____________ sharing of the e- pair polar covalent bonds: ________________ sharing of the e- pair ionic bonds: a ___________ of e-’s from the metal to the nonmetal How To Determine the Bond Type Bond type is based on the electronegativity _____________ between the two bonded atoms. (See p.403 for electronegativity values.) difference

20. Figure 12.4 The three possible types of bonds. nonpolar polar ionic

21. nonpolar polar ionic 2.5 3.5 0.9 3.0 2.5 2.1 How To Determine the Bond Type 0 to 0.4 = ______________ covalent bond 0.5 to 2.0 = _____________ covalent bond Above 2.0 = _______________ bond Practice Problems: Determine the type of bond that forms between the atoms in the following compounds. a) CO2 b) NaCl c) CH4 1.0 = polar covalent 2.1 = ionic 0.4 = nonpolar covalent

22. + – dipole shape Polarity of Molecules nonpolar polar One side is slightly (__) and the other side is slightly (__). Polar molecules are also known as _______________. Polarity depends on the __________ and symmetry of the molecule. symmetrical molecules (looks the same on all sides)= ___________ asymmetrical molecules = ___________ Polar molecules are moved by ____________ charges. (DEMO!) static

23. Molecular Polarity symmetrical tetrahedral asymmetrical pyramid asymmetrical bent asymmetrical linear symmetrical trigonal planar nonpolar polar polar polar nonpolar Practice Problems: Determine if the following molecules are polar or nonpolar based on their shape. a) CH4 b) NH3 c) H2O d) HCl e) BF3 Dipole of NH3 Dipole of H2O

24. break less less Bond Dissociation Energy most released This is the energy needed to ___________ the bond. Generally, the longer the bond, the _____ energy it takes to break it. Single bonds take ________ energy to break than double bonds and triple bonds require the _________ energy to break. When bonds form, energy is _____________. (Breaking bonds requires the addition of energy.)

25. Bond Dissociation Energy

26. weak Van der Waals condense Intermolecular Attractions The __________ attractions between one molecule and another are called _______ ______ ________ forces. They cause gas particles to stick together and _______________ at low temperatures.

27. Dispersion electron stronger more Dispersion Forces − exist between all types of molecules −This force causes Br2 to be a liquid and I2 to be a solid at room temperature. There are two types of intermolecular forces: (1) ____________________ forces: (the weaker type) caused by random _______________ motion generally _____________ with ________ electrons in the molecule

28. Dipole + – Dipole Interaction Forces (2) ____________ interactions: (the stronger force) caused by the attraction of the (__) side of one polar molecule and the (__) side of a different polar molecule

29. Hydrogen N O F Hydrogen Bonds Hydrogen Bonding in Water “________________ Bonds” are a special type of dipole interaction. They occur between the hydrogen of one polar molecule and the ____, ___ or ___ of another polar molecule.

30. Hydrogen Bonds The ladder rungs in a DNA molecule are hydrogen bonds between the base pairs, (AT and GC).

31. Hydrogen Bonds in DNA

32. metals valence nonmetal Ionic Bonding & Ionic Compounds cation anion Ionic Bonds Form when ___________ transfer their _____________ electrons to a _______________. The forces of attraction between the ____________ (+) and the _____________ (-) bind the compound together. How to Represent an Ionic Bond Electron Configuration: Na 1s2 2s2 2p6 3s1 Cl 1s2 2s2 2p6 3s2 3p5 Na… ___ 3s ↑ Cl… ___ ___ ___ ___ 3s 3p ↓ ↑ ↑ ↓ ↑ ↓ ↓

33. Na+1 Cl -1 How to Represent an Ionic Bond 2) Electron Dot Notations: Na + Cl [ ] [ ] Practice Problems:(1) Draw the electron dot notation for the formation of an ionic compound between sodium and oxygen. (2) Draw the electron configuration notation for the formation of an ionic compound between magnesium and fluorine.

35. K [K+1] Practice Problems: 3) a) Draw the electron dot notation for a potassium atom. b) Draw the electron dot notation for a potassium ion. (4) a) Draw the electron dot notation for a sulfur atom. b) Draw the electron dot notation for a sulfur ion. S [ S -2]

36. Ionic: • _______________ of electricity when dissolved water or melted. • formed between __________ and _________________ • have _________ melting points • usually ________ soluble in water • form ___________________ solids Conductors metals nonmetals Properties of Ionic Compounds and Covalent Molecules high (dissolved salt) very ionic crystalline

37. Figure 15.1-- Polar water molecules interacting with positive and negative ions of a salt.

38. Crystalline Patterns

39. Molecular: • ________________ of electricity • formed between two _______________ • usually have ________ melting points • solubility in water _______: (polar =dissolve; nonpolar = insoluble) • For a compound to to conduct electricity it must have: • (1) Charged Particles (________) • (2) Particles Free to Move (___________ or __________ phase) Insulators Properties of Ionic Compounds and Covalent Molecules nonmetals low varies ions liquid aqueous

40. Demonstration great conductor good conductor PureH2O poor conductor nonconductor