Chemical Bonding Review Molecules Salts & Formula Units Chemical Bonding Review Chemical Bonds: Forces that hold molecules and formula units together.

- + Ionic Bonding IONIC BOND Na 11 p+ 11 e- Cl 17 p+ 17 e- Electron Transfer Between Neutral Atoms 1e- Cl- 17 p+ 18 e- - Na+ 11 p+ 10 e- + Electron Transfer Forms a sodium cation and a chlorine anion. IONIC BOND Opposite Charges ATTRACT! …and this is the …..

Ionically Bonded Substances: Metal/Non-metal Combinations What does the reaction of Na(s) metal and Cl2(g) look like? (movie) 2 Na(s) + Cl2(g)  2 NaCl(s) + Energy (exothermic) In Back Cl- Na+ Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Cl- Na+ Crystal Lattice: 3 dimensional regular arrangement of points. Each point has identical surroundings. In Front

Ionically Bonded Substances: Metal/Non-metal Combinations Each Cl- or Na+ is shared with 6 neighbors. There is no unique NaCl combination. Therefore the written formula is the simplest RATIO of elements Cl- Na+ Na+ Cl- Na+ Cl- Na+ Cl- 1 Na : 1 Cl Na+ Cl- Na+ Cl- Cl- Na+ And we write the FORMULA UNIT as NaCl

Covalent Bonding Potential Energy Separation Distance H atom H atom Atoms far apart? Electrons Repel High Potential energy Still Closer? Nuclei repel each other. High Potential E. Closer together? Nuclei are attracted to “SHARED ELECTRONS” Attraction = COVALENT BOND Low Potential Energy H atom H atom H atom

H2 Crystal Lattice